Abstract

Thermally induced chemical decomposition of organic materials in the absence of oxygen is defined as pyrolysis. This process has four major application areas: (i) production of carbon materials, (ii) fabrication of pre-patterned micro and nano carbon-based structures, (iii) fragmentation of complex organic molecules for analytical purposes and (iv) waste treatment. While the underlying process principles remain the same in all cases, the target products differ owing to the phase and composition of the organic precursor, heat-treatment temperature, influence of catalysts and the presence of post-pyrolysis steps during heat-treatment. Due to its fundamental nature, pyrolysis is often studied in the context of one particular application rather than as an independent operation. In this review article, an effort is made to understand each aspect of pyrolysis in a comprehensive fashion, ensuring that all state-of-the-art applications are approached from the core process parameters that influence the ensuing product. Representative publications from recent years for each application are reviewed and analyzed. Some classical scientific findings that laid the foundation of the modern-day carbon material production methods are also revisited. In addition, classification of pyrolysis, its history and nomenclature and the plausible integration of different application areas are discussed.

INTRODUCTION

Pyrolysis is the key process in carbon nanomaterial synthesis [1–4], bulk carbon production [5, 6], fabrication of carbon-based devices [7–10], fuel generation from organic waste [11–13] and molecule fragmentation for their analysis via gas chromatography–mass spectroscopy (GC–MS) [14–16]. Primary examples of the technologically significant carbon materials prepared via pyrolysis include graphene [1, 17, 18], carbon nanotubes (CNTs) [1, 19, 20], carbon fibers (CFs) [1, 21–23], diamond-like carbon (DLC) coatings [2, 24] and other industrial carbons such as glass-like carbon (GC) [7] and graphite [5].

Unlike other manufacturing materials such as metals, the production of carbon relies heavily on synthetic routes. In fact, certain carbon allotropes (e.g. GC) are exclusively synthetic. Majority of carbon manufacturing pathways are based on pyrolysis, where a suitable organic precursor is heated to elevated temperatures in an inert environment and in some cases, a catalyst. This leads to a thermal decomposition of the precursor and the release of non-carbon atoms in various forms. Owing to carbon’s high thermal stability (in the absence of oxidants), some fraction of solid carbon is always obtained as a residue or in the form of smoke. This reactive solid carbon can potentially adopt numerous microstructural configurations, depending upon the type of precursor, its decomposition pattern, applied pressure (if any), the formation pathways of the larger carbon moieties and the thermodynamic stability of pyrolysis products [12, 25]. This principle has been used for manufacturing various crystalline as well as disordered carbons for several decades [26, 27]. With the advent of nanotechnology, the pyrolysis process and precursors have been optimized to yield the nano-scale one- and two-dimensional carbon structures. Modern-day chemical vapor deposition (CVD) technique designed for carbon nanomaterial synthesis is indeed based on the principle of pyrolysis [1, 28]. Interestingly, the primary reason behind the popularity of carbon in nanotechnology is the ease with which different carbon nanoforms can be deposited onto a range of substrates [6]. Needless to say, optimization of pyrolysis process is of utmost importance to anyone working in the field of carbon materials and associated technology.

Some large-scale industrial carbon materials such as graphite can be procured via mining. However, their synthetic production yields a high purity material and is therefore preferred. Pyrolysis additionally offers the possibility of tuning the microstructure of the ensuing carbon (e.g., enhancement of graphitic content [29, 30]), rendering the pyrolysis-assisted production more popular. Depending upon the type of carbon as well as the scale of reaction, these materials can be produced as films on a substrate or part [31], or as micro- and nano-scale structures that are pre-patterned employing lithographic techniques [7, 9]. The organic precursors may range from very simple molecules such as methane to a complex mixture of high molecular weight polymers and other hydrocarbons [12, 32]. Pyrolytic decomposition is also an extensively used process in the petrochemical refineries [33]. The fact that a variety of heavy hydrocarbons can be broken into smaller molecules that can be further fractionalized is utilized for decomposing the solid organic waste. Here, a mixture of organic (natural and/or synthetic) waste is often heat-treated in large-scale reactors or plants in order to produce useful chemicals [34].

A reaction is designated pyrolysis if (i) the precursor material is in the decomposition phase rather than bond formation and (ii) the cleavage of bonds is solely thermal. However, in many instances, the heat-treatment may also lead to partial bond formation along with dissociation, which cannot be clearly differentiated from pyrolysis. In certain reactions, the temperature-induced chemical modifications may not be solely thermal. For example, the presence of oxygen within the pyrolyzing precursor can lead to partial combustion of the material. Other reagents such as hydrogen may be present to dilute the precursor for prevention of excessive formation of a particular product [35]. The use of the term pyrolysis can be often found in the literature of such processes as well, which is acceptable as long as the primary decomposition mechanism is thermal. Notably, pyrolysis is different from both combustion and natural decomposition owing to its very definition.

It is evident that pyrolysis is a very versatile process, which is used in wide range of applications directly or indirectly. Unfortunately, this versatility is also responsible for the fact that this process is often studied only in the context of one specific research field [18, 36–41]. Different scientific communities may even use different nomenclature for essentially the same process. Often the connection is missing between various research fields that utilize the same principles and processes, with differences only in terms of process parameters. In this contribution, our goal is to compile a comprehensive review of the pyrolysis process that encompasses (i) its fundamental principles and mechanism, (ii) classification, (iii) process parameters and their tuning, (iv) all application areas with respective examples and finally, (iv) a comparison and possible integration of different application areas. This is particularly of interest for the development of energy materials and systems, which rely on pyrolysis in many ways.

HISTORY AND NOMENCLATURE

History

The use of pyrolysis for technological applications dates back to almost two centuries when carbon filaments for incandescent lamps were reportedly derived from cellulose fibers extracted from cotton and bamboo [26]. Hollow carbon filaments similar to CNTs were observed as early as in 1952, which were formed by the thermal decomposition of gaseous hydrocarbons in a closed retort [27, 42]. Single crystal graphite (now known as graphene) was produced by thermal decomposition of acetylene around the same time [43]. Some early primary batteries utilized during the WW-II contained pyrolytic carbon materials (e.g. charcoal) in the electrodes of the Leclanché cell [44].

Pyrolysis is also responsible for the formation of carbonaceous materials below the Earth’s crust, which is integrated with the carbon cycle. In fact, an entire branch of carbon science, Deep Carbon study, is dedicated to understanding the fate of different types of organic materials under harsh geophysical and environmental conditions [45]. These so-called deep carbons constitute approximately 90% of the Earth’s total carbon [45]. Such investigations reveal the possible pathways of formation of different carbon allotropes due to tectonic movements, sudden changes in the temperatures, meteorite impacts, high-pressure as well as other extreme conditions. Formation of graphite in the sedimentary rocks is believed to have originated from the organic matter trapped within rocks, where each pore of the rock may have served as a ‘reaction chamber’, thus facilitating pyrolysis over millions of years [46, 47]. Various carbon allotropes are present at varying depths under the Earth’s crust, depending upon the different temperature and pressure conditions experienced by the initial organic matter.

Nomenclature

The term pyrolysis should only be used to allude to chemical reactions taking place at temperature significantly higher than the ambient temperature in order to differentiate between pyrolysis and natural chemical decomposition. A chemical reaction taking place between 100°C and 300°C, for example, may simply be called thermal degradation rather than pyrolytic decomposition, which typically takes place between 300°C and 800°C. Pyrolysis is also often associated with burning. Burning is a complex combination of combustion, pyrolysis due to heat generated by combustion, evolution of volatile compounds, steam distillation, aerosol formation, etc. [48]. A clear distinction between the processes of pyrolysis and combustion during burning is extremely difficult because the formation of free radicals during the reaction with oxygen can be involved in the pyrolytic decomposition of molecules [48]. In addition, the free radicals formed from molecules due to heat (pyrolysis) can be the initiators of a combustion process [49]. Any organic material undergoing combustion at some stage undergoes pyrolysis to produce gaseous fuels to further initiate the combustion process and generally yields very small molecules like H2O, CO2, CO and N2 [50]. Therefore, utmost care must be taken while differentiating between these high-temperature processes as well as their nomenclature.

In the context of polymeric carbon research, the terms pyrolysis and carbonization are often used interchangeably. Notably, pyrolysis of a polymer produces tars, gases as well as solid carbon (also see the ‘Waste treatment via pyrolysis’ section). If the intended final product is carbon, pyrolysis can be considered as the pathway to carbonization. However, carbonization is the process that entails C–C bond formation that generally takes place between 800°C and 2000°C. If the material is heated further, this region (2000–3000°C) is referred to as graphitization [51]. There are examples of pyrolysis of coal to extract tars [52], volatile organic compounds (VOCs) [53] and char (carbon with impurities) [54] where each product has its own industrial relevance. This type of pyrolysis is more common for petroleum products. As such, both pyrolysis and carbonization are thermolysis processes but with different target products. Similarly, in the case of pyrolysis of light/gaseous hydrocarbons, the overall process is known as CVD. Importantly, the first step of the CVD process is pyrolysis, which is followed by the collection, migration and deposition/growth of the desired carbon nanomaterial. Discrepancies pertaining to nomenclature of these carbon nanomaterials are also relevant for carbon scientists. However, this vast topic is beyond the scope of this article. Interested readers may find the recommendations by Bianco et al. [55] helpful.

CLASSIFICATION OF PYROLYSIS PROCESS

Pyrolysis can be classified based on (i) the phase of precursor, (ii) scale of reaction (which determines the type of reactor) and (iii) target product(s), as illustrated in Fig. 1. Based on the precursor, pyrolysis can be classified into solid, liquid and gas phase. Solid phase pyrolysis primarily utilizes synthetic and natural polymers [13, 56], solid petrochemicals such as coals and cokes [54] and hydrocarbons of mixed compositions such as biomass [40, 57] or municipal solid waste (MSW) [58, 59]. Production of mesophase carbons [a precursor for meso-carbon micro beads (MCMB), carbon foams, etc.] and the production of CF by pyrolysis of petroleum pitches [60] and naphthenic residues [61] fall under the category of liquid state pyrolysis. Notably, polymers are often in their liquid state when they are patterned or spun. But before their heat-treatment, they are typically cross-linked, dried and stabilized. Some precursors such as pitches may however be in the semi-solid state also during their heat treatment. Examples of further pyrolytic cracking of pyrolysis oil (the tarry product generated during waste pyrolysis) are also carried out with a liquid precursor [62]. Gas phase pyrolysis relies on the principle of cracking a hydrocarbon gas such as methane or acetylene at sufficiently high temperatures followed by the collection of solid carbon deposits onto a substrate. As the precursor is present in gas (vapor) phase, this entire process (pyrolysis followed by material deposition and film growth) is known as the CVD. CVD is a more general term that is also applicable to various other chemicals that yield non-carbon element or compound deposits. In the case of carbon materials, however, the precursor gas is essentially a hydrocarbon, and hence, the fundamental process responsible for the CVD is pyrolysis.

Different classification pathways of pyrolysis process.
Figure 1:

Different classification pathways of pyrolysis process.

The second type of classification is based on the reaction scale and reactor type/size. Laboratory scale heat-treatment can be performed in a tube furnace, small reactors or chambers that can facilitate a controlled environment (e.g. inert gas or vacuum) [9, 11, 18, 63]. In some cases, the size of the precursor sample may be extremely small (micro or even nano-gram scale), for example, in the case of analytical pyrolysis [64] used for fossils, and in situ pyrolysis investigations performed on a transmission electron microscope (TEM) [65]. Here, the pyrolysis chamber is associated with another instrument, that may entail specially designed chips [66], wires [67] or customized sample holders [68]. Industrial pyrolysis is either used for large-scale carbon material production or for the purpose of waste treatment. In waste pyrolysis, the availability of waste determines if the process should be batch or continuous. The feed waste is often pelletized prior to pyrolysis [69]. The common reactors used for waste pyrolysis are rotary kilns [70], fixed bed [71], fluidized bed [72], tubular and certain batch and semi-batch reactors [73]. Plasma is also used for waste pyrolysis, which requires a specialized plasma reactor [73, 74]. Based on the target product, pyrolysis can be divided into three main classes: (i) carbon production, (ii) pyrolysis oil and synthetic gas production and (iii) hydrocarbon fragmentation for analytical purposes. Carbon production can be further divided into synthesis of nanomaterials, preparation of large-scale industrial carbons and carbon-conversion of polymer structures intended for device application. Details on each type of pyrolysis process will be discussed in subsequent sections.

PYROLYSIS MECHANISM

Pyrolysis typically involves covalent bond dissociation and rearrangement, which takes place between 300°C and 800°C for most hydrocarbons. The mechanism may range from simple to very complex, depending upon the nature of the precursor. For example, methane can yield some carbon species along with hydrogen slightly above the temperature where its energy of formation becomes positive [75]. A polymer, on the other hand, may exhibit complicated fragmentation patterns with parallel secondary and tertiary reactions and release volatile byproducts. Salient features of light and heavy hydrocarbon pyrolysis are described below.

Pyrolysis of light hydrocarbon

Pyrolysis of hydrocarbon gases such as methane, ethane, acetylene and low boiling point liquids such as alcohols is carried out for the purpose of carbon nanomaterial production during their CVD [35, 76, 77]. A hydrocarbon molecule disintegrates at a temperature where its free energy of formation (ΔGf) becomes positive [75]. Since, at all temperatures, finite partial pressure of various hydrocarbons is in equilibrium with hydrogen and solid carbon, its pyrolytic disintegration can never quantitatively lead to the formation of only carbon and hydrogen [78]. The equilibrium compositions are attainable only above the disintegration temperature for a particular hydrocarbon. The carbon solubility (total amount of gaseous hydrocarbons in equilibrium with carbon and hydrogen) reaches a minimum at a certain temperature for a given total pressure of the reaction chamber [78], which plays an important role in determining the optimum process pressure as well as the type of catalyst for carbon collection. At the temperatures corresponding to this carbon solubility minima, a spontaneous decomposition of the hydrocarbon takes place. Below this, the attainment of equilibrium is very slow. Consequently, other thermodynamically unstable hydrocarbons may exist in the reaction chamber [32].

For example, at pressure 102 bar and temperature >500°C, the cracking of methane becomes thermodynamically feasible. This leads to the formation of ‘carbon smoke’ in the chamber, which contains various carbon species including thermodynamically unstable ones (i.e. radicals, carbon moieties having two to eight atoms and some cyclic structures). Around 900°C, methane gas approaches equilibrium with these solid carbon species and hydrogen, that is carbon solubility in gas phase exhibits a minimum. Hence, even though thermodynamics suggest that methane disintegrates at temperatures >500°C), solid carbon deposits are only obtained around 900°C [32]. These carbon deposits are collected on to a catalytic substrate in the form of carbon films, tubes or other nano structures [31]. The catalyst plays an important role in determining the film growth rate, film thickness as well as the termination of reaction [79]. Further details on various catalysts are provided in the ‘Carbon nanomaterial synthesis’ section. Overall, the formation of carbon from light hydrocarbons follows three main reaction stages: (i) cracking of aliphatic hydrocarbons into smaller molecules or reactive species, (ii) cyclization of hydrocarbon chains to form aromatics and (iii) condensation of these aromatics to form polycyclic aromatics on a suitable substrate [32].

Pyrolysis of high molecular weight hydrocarbon

High molecular weight hydrocarbons include polymers, pitches, cokes and their mixtures. Their pyrolysis can be understood in terms of both chemical and physical changes, as discussed below.

Chemical aspects

During heavy hydrocarbon pyrolysis, a series of primary, secondary and tertiary reactions take place in parallel in a highly dynamic system [25, 80, 81]. The primary chemical changes that occur (generally in sequence) typically include (i) cleavage of C-heteroatom bonds to generate free radicals, (ii) molecular re-arrangement, (iii) thermal polymerization (iv) aromatic condensation and (v) elimination of H2 from the side chains [81]. The bond cleavage is based on the bond dissociation energies (BDEs) of the specific carbon-heteroatom bond. Although these reactions take place in parallel, only one of them is dominant at a particular pyrolysis temperature [82, 83]. For example, when we pyrolyze coal, at around 300–400°C, condensable coal-tar is released along with other volatiles due to reaction type (i), but at the same time, steps (ii) and (iii) occur in the remaining solid. With increasing temperature, step (iii) becomes dominant over other two steps and char or coke is obtained around 800°C [82]. One can terminate the heat-treatment process at any temperature, allowing only few of the aforementioned steps to complete. For treatment of waste, for example, the process is terminated at step (iii); hence, the maximum pyrolysis temperature does not exceed 800°C and the final solid residue contains pores and impurities [13].

In the case of carbon material production, the process is terminated after step (v). Here, the entire heat-treatment can be divided into three stages: pre-carbonation (pyrolysis), carbonization and graphitization (optional) [84]. Pre-carbonization stage encompasses breaking of C-heteroatoms bond and re-arrangement of the C–C bonds followed by dehydration and elimination of halogens below 500°C due to their lower BDEs (mostly <450 KJ/Mol−1). At this stage, a rapid weight loss is observed due to the elimination of volatiles [85] and cyclization (formation of aromatic network) [86]. Above 500°C, bonds with higher BDEs (>600 KJ/Mol−1) are broken, and oxygen and nitrogen are eliminated. However, at this stage, the thermal polymerization is dominant [81] and the aromatic networks gets interconnected, resulting in primary volume shrinkage and rapid weight loss in the solid. This phase is called ‘carbonization’ stage, which takes place at temperatures >800°C [51] and may extend up to 2000°C for some polymers. It is intuitive that an organic material of high molecular weight will decompose to form carbonaceous hydrocarbons of lower molecular weights. However, it is not always the case, as some organic molecules on pyrolysis may result in molecules larger than the starting ones. For example, during the thermal cracking of n-Hexadecane (n-C16) [87], along with the low molecular weight hydrocarbons, (alkanes (C1–C14) and olefins (C2–C15)), higher molecular weight alkyl hexadecanes and alkanes (C18–C31) are also obtained [87], which could be attributed to thermal polymerization.

Further heat-treatment above the temperature of 2000°C leads to gradual elimination of any structural defects due to aromatic condensation and the elimination of the last fragment of volatiles [81]. This stage is called the ‘graphitization’ stage, which takes place at temperatures above 2000°C [51]. Here, the crystallite diameter of residual pyrolytic carbon (La) is increased and the stack thickness (Lc) is decreased. An example of a heavy hydrocarbon precursor is poly-vinyl chloride (PVC), that undergoes all the three stages during its conversion into synthetic graphite [86].

Physical aspects

In terms of physical changes (e.g. phase, density and morphology), heavy hydrocarbons adopt one of the two possible mechanisms, known as coking and charring, during their pyrolysis. These principles are described in detail elsewhere [7]. Briefly, if the material experiences softening such that there is a liquid or semi-solid phase during its pyrolysis, it is said to undergo coking. Charring, on the other hand, refers to a relatively high rigidity and the protection of the carbon backbone in its nearly original morphology during and after its pyrolysis. These morphological aspects are of paramount importance when the target product is carbon. Precursors that undergo coking yield the carbon with an extremely flat surface and exhibit mostly microporosity. Charring leads to meso, macro as well as microporosity in the residual carbon.

Both physical and chemical aspects of pyrolysis are strongly influenced by (i) the highest process pyrolysis temperature, (ii) temperature ramp rate and (iii) residence (dwell) time at the highest temperature. The effect of these parameters on the composition and microstructure of the pyrolysis products is detailed in sections ‘Carbon nanomaterial synthesis’ and ‘Waste treatment via pyrolysis.’

Characterization of polymer pyrolysis

Physicochemical changes occurring during heat-treatment of a polymer can be studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and by characterization of the material produced at different temperature points. One can also chemically analyze the volatile byproducts generated during the process via GC–MS [64]. Oils or tars can be separately collected using a condenser unit and then be further analyzed. Other characterization techniques such as elemental analysis, Raman spectroscopy, X-ray diffraction and neutron diffraction can be used for understanding the residual carbon [65, 88–92].

In the recent past, some methods for observing the microstructural changes during the heat-treatment (insitu) have also been developed. Figure 2 is a collection of TEM, TGA, XRD and wide-angle neutron scattering (WANS)/wide angle X-ray scattering (WAXS) data that indicate the microstructural changes taking place in the solid residue during pyrolysis, which ultimately converts into different types of carbon. It can be clearly observed from the TEM images (Fig. 2A and B) that between 600°C and 800°C the material undergoes major microstructural changes and its fragments display a high mobility [65, 88]. This is also supported by electrical and mechanical property tests of these intermediate materials [93]. TGA analysis (Fig. 2C) of cellulose indicates that there is a significant mass loss between 300°C and 400°C [89]. XRD data show an increased peak intensity from the (002) and (100) planes, suggesting a better order and crystallite growth in the resulting carbon with an increase in pyrolysis temperature in the range 500–900°C. It also reveals the shifting of the (002) peaks to higher angles with increasing temperatures (Fig. 2D) [90]. The exsitu WANS and WAXS data for carbon obtained from (poly)-furfuryl alcohol also confirm an increased order due to the annealing of some of the defects (Fig. 2E) [91]. Some other techniques used for insitu observations of pyrolysis include a study of planetary materials by Raman Spectroscopy integrated with Laser-heating [92].

In situ TEM images of a pyrolyzing SU-8 thin-film up to 1200°C, scale bars—1 nm (A), reproduced with permission from Sharma et al. [65]; TEM images of in-situ heating of photoresist, S1805 showing migration and merging of a small graphitic domains at various temperatures (B), reproduced with permission from Shyam Kumar et al. [88]; TG–DTG curves of in-situ pyrolysis of cellulose at a heating rate of 5°C/min (C), reproduced with permission from Zhu et al. [89]; in-situ XRD studies of pyrolysis of coals at various temperatures (XRD diffractograms) (D), reproduced with permission from Li et al. [90]; (ex-situ) WANS AND WAXS data of pyrolysis of poly-furfuryl alcohol at various temperatures (E), reproduced with permission from Jurkiewicz et al. [91]. TG-DTG, thermogravimetry-differential thermogravimetry.
Figure 2:

In situ TEM images of a pyrolyzing SU-8 thin-film up to 1200°C, scale bars—1 nm (A), reproduced with permission from Sharma et al. [65]; TEM images of in-situ heating of photoresist, S1805 showing migration and merging of a small graphitic domains at various temperatures (B), reproduced with permission from Shyam Kumar et al. [88]; TG–DTG curves of in-situ pyrolysis of cellulose at a heating rate of 5°C/min (C), reproduced with permission from Zhu et al. [89]; in-situ XRD studies of pyrolysis of coals at various temperatures (XRD diffractograms) (D), reproduced with permission from Li et al. [90]; (ex-situ) WANS AND WAXS data of pyrolysis of poly-furfuryl alcohol at various temperatures (E), reproduced with permission from Jurkiewicz et al. [91]. TG-DTG, thermogravimetry-differential thermogravimetry.

APPLICATIONS OF PYROLYSIS

A summary of applications of pyrolysis along with the associated manufacturing pathways is presented in Fig. 3. Table 1 contains the typical temperature range and pyrolysis environment used in these different applications. As most of the application areas are rapidly progressing, one can find some variations in pyrolysis conditions for specific cases. We have summarized the typical values here. In the subsequent sections, we review the representative examples from each application area.

schematic representation of classification of applications of pyrolysis into four major areas: (A) carbon material production, (B) fabrication of carbon-micro nano devices, (C) chemical analysis of unknown samples by Py-GC–MS, (D) treatment of waste. CNF, carbon nanofibers; HOPG, highly oriented pyrolytic graphite.
Figure 3:

schematic representation of classification of applications of pyrolysis into four major areas: (A) carbon material production, (B) fabrication of carbon-micro nano devices, (C) chemical analysis of unknown samples by Py-GC–MS, (D) treatment of waste. CNF, carbon nanofibers; HOPG, highly oriented pyrolytic graphite.

Table 1:

Typical temperature range and other parameters pertaining to different applications of pyrolysis

S. NoApplication areaPyrolysis conditionsTarget product and remarksRef.
1.Carbon material production600–1200°C, deposition on catalytic substrateCarbon nanomaterials by CVD (Graphene, CNT, VGCF)[1]
350–600°C, in the presence of plasmaDLC coatings by PECVD[94, 24]
900–2800°CSpun CFs; graphitic content in fibers is enhanced at high temperatures[22,95]
2500–3000°CHighly oriented pyrolytic graphite (HOPG) can also be prepared at lower temperatures under stress; precursor: pyrolytic graphite[5]
2000–3000°CBulk GC; lower temperatures yield material with lower purity[51]
900–1000°CPorous carbons that can be further activated[96]
500–1000°CMesophase carbons (pitch and coke pyrolysis)[97]
2.Fabrication of carbon-based micro-nano devices900–1100°CPrecursors: high carbon containing, lithography compatible polymers[7]
3.Analytical pyrolysis300–1000°CFragmented hydrocarbons are analyzed using Py-GC–MS[67,98]
4.Waste treatment400–500°CAlmost equal proportion of char, pyro-oil, and syngas are obtained[12]
500–700°CPyro-oil, major product. Often sold as an alternative fuel (obtained from plastic waste)[13,12]
>700°CSyngas, the major product[58, 99]
S. NoApplication areaPyrolysis conditionsTarget product and remarksRef.
1.Carbon material production600–1200°C, deposition on catalytic substrateCarbon nanomaterials by CVD (Graphene, CNT, VGCF)[1]
350–600°C, in the presence of plasmaDLC coatings by PECVD[94, 24]
900–2800°CSpun CFs; graphitic content in fibers is enhanced at high temperatures[22,95]
2500–3000°CHighly oriented pyrolytic graphite (HOPG) can also be prepared at lower temperatures under stress; precursor: pyrolytic graphite[5]
2000–3000°CBulk GC; lower temperatures yield material with lower purity[51]
900–1000°CPorous carbons that can be further activated[96]
500–1000°CMesophase carbons (pitch and coke pyrolysis)[97]
2.Fabrication of carbon-based micro-nano devices900–1100°CPrecursors: high carbon containing, lithography compatible polymers[7]
3.Analytical pyrolysis300–1000°CFragmented hydrocarbons are analyzed using Py-GC–MS[67,98]
4.Waste treatment400–500°CAlmost equal proportion of char, pyro-oil, and syngas are obtained[12]
500–700°CPyro-oil, major product. Often sold as an alternative fuel (obtained from plastic waste)[13,12]
>700°CSyngas, the major product[58, 99]
Table 1:

Typical temperature range and other parameters pertaining to different applications of pyrolysis

S. NoApplication areaPyrolysis conditionsTarget product and remarksRef.
1.Carbon material production600–1200°C, deposition on catalytic substrateCarbon nanomaterials by CVD (Graphene, CNT, VGCF)[1]
350–600°C, in the presence of plasmaDLC coatings by PECVD[94, 24]
900–2800°CSpun CFs; graphitic content in fibers is enhanced at high temperatures[22,95]
2500–3000°CHighly oriented pyrolytic graphite (HOPG) can also be prepared at lower temperatures under stress; precursor: pyrolytic graphite[5]
2000–3000°CBulk GC; lower temperatures yield material with lower purity[51]
900–1000°CPorous carbons that can be further activated[96]
500–1000°CMesophase carbons (pitch and coke pyrolysis)[97]
2.Fabrication of carbon-based micro-nano devices900–1100°CPrecursors: high carbon containing, lithography compatible polymers[7]
3.Analytical pyrolysis300–1000°CFragmented hydrocarbons are analyzed using Py-GC–MS[67,98]
4.Waste treatment400–500°CAlmost equal proportion of char, pyro-oil, and syngas are obtained[12]
500–700°CPyro-oil, major product. Often sold as an alternative fuel (obtained from plastic waste)[13,12]
>700°CSyngas, the major product[58, 99]
S. NoApplication areaPyrolysis conditionsTarget product and remarksRef.
1.Carbon material production600–1200°C, deposition on catalytic substrateCarbon nanomaterials by CVD (Graphene, CNT, VGCF)[1]
350–600°C, in the presence of plasmaDLC coatings by PECVD[94, 24]
900–2800°CSpun CFs; graphitic content in fibers is enhanced at high temperatures[22,95]
2500–3000°CHighly oriented pyrolytic graphite (HOPG) can also be prepared at lower temperatures under stress; precursor: pyrolytic graphite[5]
2000–3000°CBulk GC; lower temperatures yield material with lower purity[51]
900–1000°CPorous carbons that can be further activated[96]
500–1000°CMesophase carbons (pitch and coke pyrolysis)[97]
2.Fabrication of carbon-based micro-nano devices900–1100°CPrecursors: high carbon containing, lithography compatible polymers[7]
3.Analytical pyrolysis300–1000°CFragmented hydrocarbons are analyzed using Py-GC–MS[67,98]
4.Waste treatment400–500°CAlmost equal proportion of char, pyro-oil, and syngas are obtained[12]
500–700°CPyro-oil, major product. Often sold as an alternative fuel (obtained from plastic waste)[13,12]
>700°CSyngas, the major product[58, 99]

Carbon nanomaterial synthesis

CVD of carbon nanomaterials such as graphene, CNTs, vapour grown CF (VGCFs), VD diamonds and DLC films is based on the principle of pyrolysis [28], where a gaseous hydrocarbon is pyrolyzed. Historically, CVD and similar processes were used for carbon production as early as the 19th century [26, 43, 100]. However, various pyrolytic carbon materials were only considered as byproducts, as the ultimate goal was to synthesize graphite. Only in the last few decades the potential of carbon nanomaterials was recognized and they were studied as independent materials. Experimental work on single (2D) crystals of graphite was reported in the 1960s [43, 101]. Prior to its synthesis, the electronic properties of this so-called 2D-graphite were theoretically studied in 1947 by Wallace [102]. Graphene-oxide, another derivative of single crystal graphite, was reported as early as 1859 [103] in a different context. The term ‘graphene’ was added to the IUPAC database in 1994, based on its experimental preparation reported in 1962 [101]. In 2004, Novoselov et al. [104] developed a novel method for obtaining graphene from HOPG by mechanical exfoliation, for which they were awarded the Nobel prize in 2010. With advances in nano-scale characterization techniques and extensive ongoing research across the globe, graphene has become one of the most technologically important materials of the 21st century. Apart from graphene, other carbon nanomaterials CNTs [105], VGCFs [21, 106] and DLC [2] are also of immense technological significance. They are also prepared via pyrolysis of gaseous or light liquid hydrocarbons. The pyrolysis conditions as well as the morphology and type of catalytic substrates may differ in these cases. Table 2 contains the standard CVD parameters for synthesis of various carbon nanomaterials. More specific details are discussed below. As there are multiple detailed review articles and books available for each individual nanomaterial, we have only provided the details of their synthesis that fit in the scope of this review. For further reading, relevant reference material is suggested.

Table 2:

Carbon nanomaterials synthesized by gas phase pyrolysis (CVD) and their process parameters

S. No.Carbon nanomaterialPrecursor gasPyrolysis parametersRef.
1.Single-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; Cu, single crystal Ni,

  • Cu–Ni binary alloys, thin films.

  • He gas

[1, 18]
2.Multi-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; polycrystalline Ni thin films,

  • He gas

[1, 18]
3.SWCNT
  • CH4 + H2

  • CH4 + Ar,

  • camphor (Industrial Production)

  • CVD, temperature; 700–1200°C,

  • catalyst; Fe, Ni, Co, Fe2O3

  • nanoparticles (<10 nm)

[1, 107, 108]
4.MWCNTC6H6, C2H4 + N2
  • CVD, temperature; 550–850°C,

  • catalyst; Fe, Ni–Cu nanoparticles

[1, 107]
5.VGCF
  • C6H6, C3H8, C2H2,

  • Ferrocene

  • CVD, temperature; 500–1500°C,

  • catalyst; Fe, Co, Ni, Au, Fe–Ni, Ni–Cu

  • nanoparticles >20 nm

[1, 21]
6.VDDsCH4 + H2/O2
  • Filament-assisted thermal CVD,

  • Filament temperature; 2200°C

  • Substrate temperature; 600–1200°C,

  • Pressure; 3–4 kPa,

  • Diamond or non-diamond substrates

[2]
C2H2 + O2
  • Combustion-flame-assisted CVD,

  • substrate temperature; 600–1200°C

7.DLC filmsCH4, C2H2
  • PECVD,

  • Temperature 350–600°C (metals and alloys coatings)

[24, 94]
8.FullerenesCH4 + H2
  • Hot filament CVD,

  • Filament temperature; 2000–2200°C,

  • Substrate temperature; 950–1000°C

[1, 109]
C2H2 + Ar + H2
  • Microwave-enhanced CVD,

  • Substrate temperature; 950–1000°C

S. No.Carbon nanomaterialPrecursor gasPyrolysis parametersRef.
1.Single-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; Cu, single crystal Ni,

  • Cu–Ni binary alloys, thin films.

  • He gas

[1, 18]
2.Multi-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; polycrystalline Ni thin films,

  • He gas

[1, 18]
3.SWCNT
  • CH4 + H2

  • CH4 + Ar,

  • camphor (Industrial Production)

  • CVD, temperature; 700–1200°C,

  • catalyst; Fe, Ni, Co, Fe2O3

  • nanoparticles (<10 nm)

[1, 107, 108]
4.MWCNTC6H6, C2H4 + N2
  • CVD, temperature; 550–850°C,

  • catalyst; Fe, Ni–Cu nanoparticles

[1, 107]
5.VGCF
  • C6H6, C3H8, C2H2,

  • Ferrocene

  • CVD, temperature; 500–1500°C,

  • catalyst; Fe, Co, Ni, Au, Fe–Ni, Ni–Cu

  • nanoparticles >20 nm

[1, 21]
6.VDDsCH4 + H2/O2
  • Filament-assisted thermal CVD,

  • Filament temperature; 2200°C

  • Substrate temperature; 600–1200°C,

  • Pressure; 3–4 kPa,

  • Diamond or non-diamond substrates

[2]
C2H2 + O2
  • Combustion-flame-assisted CVD,

  • substrate temperature; 600–1200°C

7.DLC filmsCH4, C2H2
  • PECVD,

  • Temperature 350–600°C (metals and alloys coatings)

[24, 94]
8.FullerenesCH4 + H2
  • Hot filament CVD,

  • Filament temperature; 2000–2200°C,

  • Substrate temperature; 950–1000°C

[1, 109]
C2H2 + Ar + H2
  • Microwave-enhanced CVD,

  • Substrate temperature; 950–1000°C

SWCNT, single-walled CNTs, MWCNTs, multi-walled CNTs, VGCF, vapour grown CF.

Table 2:

Carbon nanomaterials synthesized by gas phase pyrolysis (CVD) and their process parameters

S. No.Carbon nanomaterialPrecursor gasPyrolysis parametersRef.
1.Single-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; Cu, single crystal Ni,

  • Cu–Ni binary alloys, thin films.

  • He gas

[1, 18]
2.Multi-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; polycrystalline Ni thin films,

  • He gas

[1, 18]
3.SWCNT
  • CH4 + H2

  • CH4 + Ar,

  • camphor (Industrial Production)

  • CVD, temperature; 700–1200°C,

  • catalyst; Fe, Ni, Co, Fe2O3

  • nanoparticles (<10 nm)

[1, 107, 108]
4.MWCNTC6H6, C2H4 + N2
  • CVD, temperature; 550–850°C,

  • catalyst; Fe, Ni–Cu nanoparticles

[1, 107]
5.VGCF
  • C6H6, C3H8, C2H2,

  • Ferrocene

  • CVD, temperature; 500–1500°C,

  • catalyst; Fe, Co, Ni, Au, Fe–Ni, Ni–Cu

  • nanoparticles >20 nm

[1, 21]
6.VDDsCH4 + H2/O2
  • Filament-assisted thermal CVD,

  • Filament temperature; 2200°C

  • Substrate temperature; 600–1200°C,

  • Pressure; 3–4 kPa,

  • Diamond or non-diamond substrates

[2]
C2H2 + O2
  • Combustion-flame-assisted CVD,

  • substrate temperature; 600–1200°C

7.DLC filmsCH4, C2H2
  • PECVD,

  • Temperature 350–600°C (metals and alloys coatings)

[24, 94]
8.FullerenesCH4 + H2
  • Hot filament CVD,

  • Filament temperature; 2000–2200°C,

  • Substrate temperature; 950–1000°C

[1, 109]
C2H2 + Ar + H2
  • Microwave-enhanced CVD,

  • Substrate temperature; 950–1000°C

S. No.Carbon nanomaterialPrecursor gasPyrolysis parametersRef.
1.Single-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; Cu, single crystal Ni,

  • Cu–Ni binary alloys, thin films.

  • He gas

[1, 18]
2.Multi-layer grapheneCH4 + H2, C2H2, C6H6
  • CVD, temperature; 500–1000°C,

  • catalyst; polycrystalline Ni thin films,

  • He gas

[1, 18]
3.SWCNT
  • CH4 + H2

  • CH4 + Ar,

  • camphor (Industrial Production)

  • CVD, temperature; 700–1200°C,

  • catalyst; Fe, Ni, Co, Fe2O3

  • nanoparticles (<10 nm)

[1, 107, 108]
4.MWCNTC6H6, C2H4 + N2
  • CVD, temperature; 550–850°C,

  • catalyst; Fe, Ni–Cu nanoparticles

[1, 107]
5.VGCF
  • C6H6, C3H8, C2H2,

  • Ferrocene

  • CVD, temperature; 500–1500°C,

  • catalyst; Fe, Co, Ni, Au, Fe–Ni, Ni–Cu

  • nanoparticles >20 nm

[1, 21]
6.VDDsCH4 + H2/O2
  • Filament-assisted thermal CVD,

  • Filament temperature; 2200°C

  • Substrate temperature; 600–1200°C,

  • Pressure; 3–4 kPa,

  • Diamond or non-diamond substrates

[2]
C2H2 + O2
  • Combustion-flame-assisted CVD,

  • substrate temperature; 600–1200°C

7.DLC filmsCH4, C2H2
  • PECVD,

  • Temperature 350–600°C (metals and alloys coatings)

[24, 94]
8.FullerenesCH4 + H2
  • Hot filament CVD,

  • Filament temperature; 2000–2200°C,

  • Substrate temperature; 950–1000°C

[1, 109]
C2H2 + Ar + H2
  • Microwave-enhanced CVD,

  • Substrate temperature; 950–1000°C

SWCNT, single-walled CNTs, MWCNTs, multi-walled CNTs, VGCF, vapour grown CF.

Graphene

Graphene is defined as a defect-free single layer of graphite. This material can also be prepared via mechanical or electrochemical exfoliation of HOPG (also see the section ‘Highly oriented pyrolytic graphite’) [104]. However, CVD is a bottom-up fabrication technique that is preferred for making relatively defect-free, large area graphene films [6]. For this purpose, a gaseous precursor such as methane, ethylene and benzene along with an inert gas (e.g. He and N2) is fed into a reactor. The precursor gas disintegrates at approximately (600–1000°C) close to the surface of a heated catalyst (transition metals in most cases). The carbon species produced by this decomposition diffuse into the metal and precipitate out onto the metal surface, leading to nucleation and subsequent growth of graphene films. The quality of graphene can be controlled by optimizing the precursor gas flow rate, inert gas flow rate, catalyst, reaction time and the pressure inside the CVD chamber which affects the activation energy required for formation of graphene nuclei on the catalyst surface [110, 111]. The formation of single-layer or multi-layer graphene depends upon the solubility of carbon and the catalyst used in the CVD process. Transition metals with unfilled d-orbitals (e.g. Co/Ni) exhibit higher affinity for carbon atoms and hence produce multi-layer graphene by dissolution and precipitation of carbon species, whereas the ones with filled d-orbitals (e.g. Cu/Zn) feature a low affinity to carbon, hence carbon diffuses onto the surface and forms mono-layer graphene [110]. Further, details on CVD reactor variations, various catalysts used, optimum temperature for graphene growth based on precursor–catalyst combination, can be found in some recent review articles on this topic [17, 112–115]. CVD graphene is primarily used for its electrical properties after transferring it from the metal substrate to other suitable substrates [116]. For a detailed information on the applications of CVD graphene, a recent article by Saeed et al. [117] may be referred.

Carbon nanotubes

CNTs have the appearance of rolled-up single or multiple layers of graphene, which are designated as single-walled or multi-walled CNTs (SWCNTs and MWCNTs), respectively. As CNTs feature a curvature, they are occasionally also considered a part of the fullerene family of carbon. Fullerenes feature a new hybridization between sp2 and sp3 [118] as the unhybridized p-orbital lies at an angle between 90° (as in an ideal sp2 carbon material) and 109.5° (as in an ideal sp3 carbon material). CNTs are produced by CVD, which involved pyrolytic decomposition of gaseous hydrocarbons and carbon deposition (referred to as ‘growth’ in the case of tubes and fibers) on catalytic (nano)particles rather than films. The catalyst particles may be attached to a substrate (seeding catalyst method) or float in the CVD chamber (floating catalyst method) [119] which is heated to 550–1200°C. The temperature ranges for obtaining SWCNTs and MWCNTs are listed in Table 2. The carbon precursors are mostly similar to those used for graphene (e.g. methane, acetylene, ethylene and toluene) that are introduced into the chamber at a specific rate in presence of an inert gas (Ar/N2). Elemental carbon moieties diffuse into the catalyst and precipitate carbon either from the top or bottom of the catalyst particle. Typical catalysts used for CNTs are transition metals such as Fe, Co and Ni [120]. Their size determines whether the CNTs will be SW [121]. For SWCNTs growth, catalyst particles should be less than 10 nm [108]. Other process optimization parameters are synthesis temperature and pressure, reaction time and inert gas-flow rate [19, 122]. Sometimes CVD is carried out in presence of plasma to enhance the rates of the reactions taking place inside the chamber. Such a CVD process is termed as plasma-enhanced CVD (PECVD). It has been reported that with PECVD, CNTs can be produced at temperatures as low as 120°C [123]. Further information on CNT synthesis and applications can be accessed in some recent literature on this topic [20, 124–127].

Vapor grown CFs

VGCFs are nano-scale solid carbon filaments with an aspect ratio of around 100 [21, 106]. They are different from conventional bulk CF (having diameters of a few micrometers) in their preparation process and hence their properties. Their synthesis involves a hydrocarbon gas (such as natural gas, propane, acetylene, benzene, ethylene and methane) as the precursor, undergoing thermal decomposition in an inert atmosphere at around 950–1100°C on the surface of a catalyst, which are normally metal nanoparticles (Fe/Ni/Co), >20 nm in size [119, 128–130]. Similar to CNTs, the catalyst can be present onto the heated substrate or sometimes can be fed along with the precursor gas as floating catalyst [129, 131]. The catalyst particle takes up carbon from the supersaturated hydrocarbon gas and leaves out tubular filaments of mainly sp2 hybridized carbon. The formation mechanism of VGCFs is similar to the formation of CNTs, with the difference in the size of the catalyst particles used for the decomposition of the hydrocarbons [132, 133]. It is because of the catalyst size, instead of tubular cross-section in case of CNTs, fibers with the cross-section consisting of flakes of graphite layers in various orientation precipitate out of the catalyst [134, 135]. There are reports that VGCFs having high degree of graphitization can also be prepared by CVD without the use of a catalyst on the surface of ceramic substrates [106]. VGCFs are excellent candidates as filler materials for polymer matrix composites [136–138] and carbon–carbon composites [139–143]. They are also used in energy storage devices as filler in electrodes of lead-acid batteries and Li-ion batteries, and in supercapacitor applications [144, 145].

Vapor-deposited diamonds

Carbon thin films (hydrogenated or dehydrogenated) prepared via CVD and having significant portion of sp3 carbon atoms with negligible sp2 content are referred to as vapor-deposited diamonds (VDDs) [2]. The use of CVD for diamond growth started in the late 1960s ([2, 146, 147]). A breakthrough was achieved when atomic hydrogen was used for etching away the graphite deposits. This left a high content of diamond deposits on the substrate. VDDs are used as industrial coatings because of their excellent mechanical properties, especially on various cutting tools [148].

Diamond films are deposited using PECVD including filament-assisted and microwave PECVD methods [149, 150]. Plasma is required to dissociate the hydrogen molecule into reactive atomic hydrogen, which is essential for the formation of diamond instead of its thermodynamically more stable counterpart, graphite. The H atom temporarily bonds with the fourth carbon atom (in the unhybridized p-orbital) to form a tetrahedral geometry (as in the case of sp3 hybridization). This prevents the structure from forming flat sheets of trigonal planar graphite-like geometry (sp2 hybridization). The temperature of the plasma can be as high as 2000°C, but substrate is maintained at lower temperatures (<1000°C). At higher temperatures >1200°C, graphite deposits is more stable. There is no specific requirement when it comes to the substrate. Often industrial machine parts are directly coated with the VDD films. For growth of single crystal diamond, however, a diamond substrate is essential, which renders the process relatively expensive [151]. For bulk poly-crystalline diamonds, silicon is the widely used substrate [6, 151]. The growth of diamond on a non-diamond substrate requires an extra nucleation step that provides the substrate with necessary diamond seeds for diamond growth. These seeds grow three dimensionally until the grain coalesces to form a poly-crystalline film [6]. The properties of CVD diamonds films have been studied and reviewed in various old and new publications [2, 152–154]. Sometimes, along with the precursor hydrocarbon, precursors of boron(B) or phosphorus(P) is also introduced into the CVD chamber to obtain B/P doped diamonds, which are used in the semiconductor industry/power electronics [155–157].

DLC films

DLC is a metastable form of carbon, which is physically amorphous in bulk but consists of small diamond-like crystallites (composed of sp3 hybridized carbon) dispersed randomly in the matrix of sp2 carbon at the microscale. Hence, it is a disordered type of carbon. It features a higher fraction of sp2-content as well as hydrogen impurity (>50%) compared with VDDs [6] which differentiates the two. Both DLC and VDD are used in applications where their optical properties, high hardness and wear resistance can be harnessed [148, 158–160]. Some common examples include their coatings on the automotive parts [161], biomedical tools [159, 162], optical devices [158] and cutting tools [148, 163].

DLC film deposition requires a substantially lower (300°C) substrate temperature compared with VDD. Here, the plasma generation for dissociation of hydrogen molecule is induced by a high-frequency discharge [164, 165], which does not produce very high temperatures. Consequently, graphite deposits are not etched away by atomic hydrogen and significant sp2 carbon is retained in the material. Films of up to 0.5-µm thickness can be obtained on any substrates (including polymers) [6], which is an advantage of the DLC coatings over VDD. A disadvantage of DLC films is their low temperature resistance [166] that impedes their use in high-performance thermal coatings (operating temperatures >300°C). DLC coatings also feature a high residual stress and lower toughness, that limits many mechanical applications. These limitations can be overcome by doping DLC with foreign materials such as chromium [167], nitrogen [168] and silicon [169] to form DLC nanocomposites. The source of these dopants in gaseous form can be mixed with the precursor hydrocarbon gas used for DLC deposition [168], or in solid form can be deposited on the substrate by sputtering (to form an interlayer) and DLC grown on the interlayer [167]. DLC nanocomposite with Cr doping enhances the mechanical properties by improving the fracture toughness of the material [167], N and Si doping improves thermal stability of DLC coatings and reduces the friction coefficient [168, 169]. For more details on DLC nanocomposites, readers can refer to the article by Abdul et al. [163].

Manufacture of spun CFs

Another well-known application of the pyrolysis process is the fabrication of CF from various solid/semi-solid precursors (heavy hydrocarbons). CF and CF-based composites are extensively used in the aerospace [170] and automobile industries [171]. CF-based composites are also an important candidate for construction of turbine blades due to their high strength and low weight [172]. For manufacturing CFs, first a viscoelastic polymer or pitch is spun via melt-spinning or electrospinning techniques [173]. Afterward, they are converted into carbon via pyrolysis, as discussed in the ‘Pyrolysis of high molecular weight hydrocarbon’ section. This selection of polymers for fiber fabrication is restricted to those with a good viscoelasticity. PAN, pitches and rayon are a few examples of polymers that have good viscoelasticity and hence good spinnability; therefore, they are utilized in the commercial production of CFs. The microstructure of carbon obtained from the spun polymer fibers is different from the carbon obtained from bulk polymers because of a high surface-to-volume ratio of the fibers. This facilitates an easy annealing of pyrolysis by-products such as tars and gases, as well as other structural defects during the heat-treatment. CFs (even those derived from PAN having a turbostratic structure) can typically be made more graphitic at high temperatures [174] which is not possible in the case of bulk carbons. Polymers are typically spun (using melt-spinning or electrospinning processes) prior to their carbonization/pyrolysis. Details of the spinning processes as well as polymer selection of obtaining CF can be found in many reviews [175–177]. Commercial CFs are produced mainly by carbonization of PAN-based fibers and pitch fibers. Although carbonization of many other polymeric fibers of rayon, polyvinyl alcohol and poly-esters has been attempted, they are yet to hit the market expectations [178]. Figure 4 shows the electrospinning and melt spinning process for production of spun fibers followed by stabilization and carbonization to obtain CFs. Some polymers that have been employed for CF fabrication are polyacrylonitrile (PAN) [179], phenolic resins [180] and cellulose (lignin-based fibers) [181, 182] and its derivative (Rayon) [183].

Production of spun CF by different routes using different precursors. PVA, polyvinyl alcohol.
Figure 4:

Production of spun CF by different routes using different precursors. PVA, polyvinyl alcohol.

CF from polymers

Disordered carbons are hard and brittle, which makes it difficult to pull fibers out of them. The production of CF is therefore carried out by first preparing fibers using a suitable polymer and subsequently converting it into carbon via at ≥900°C. In the 1950s, rayon fibers were carbonized and used for high temperature missile applications [183, 184], but the technical breakthrough for high strength CF started in the 1960s when PAN precursor was introduced for commercial production of CFs because of its high carbon yield (approximately 50%) [185], compared with the carbon yield of rayon (approximately 30%) [184]. Nowadays PAN is the most common precursor for production of CF on a large scale due to its high carbon yield compared with other polymers and also due to that fact that the viscoelasticity of PAN can be altered/modified to produce CF of various diameters. The diameter in turn influences the graphitizability.

Electrospun PAN fibers can be converted to CF by the following steps: (i) stabilizing heat treatment at around 300°C, to prevent the precursor fibers from melting and fusion, (ii) carbonizing heat treatment at 900°C in an inert environment to drive off the majority of non-carbon elements, (iii) optional high-temperature treatment (2500°C) to improve mechanical properties of the fibers and increase the graphitic content of the fibers. Fibers undergoing steps (i) and (ii) are generally called CF and fibers undergoing all the three steps are also called graphite fibers [22]. Commercial CFs are either obtained in the form of a tow or a yarn, with each tow/yarn containing thousands of single fibers of diameter ranging from 5 to 10 µm. These fibers are either braided or woven into a mat and are commercially available as ‘preforms’. These preforms are mainly used as filler material/laminates for fabrication of polymer matrix composites [186, 187] and carbon–carbon composites [188–190].

CF from petroleum pitches

Although PAN-based CFs account for approximately 90% of the world’s CF consumption [191], the carbon yield of PAN is relatively low [185]. The search for other inexpensive raw materials as precursors for CF started in 1970s, which led to use of petroleum pitches for making precursor fibers having >70% carbon yield [192]. Their mechanical properties of pitch fibers are comparable to PAN-derived fibers and they are relatively cost effective [193].

Pitches are a byproduct of petroleum and coal processing, but can also be synthetically produced, for example, from PVC [194]. The chemical composition of pitch is very complex and is mainly a mixture of polycyclic aromatic hydrocarbons and tars. However, the composition of pitches also depends on its source [195]. Pitch-based fibers (isotropic and mesophase) [95, 196, 197] are generally processed via melt spinning to obtain pitch fibers. Pitch fibers are then stabilized/oxidized followed by carbonization to obtain CFs [198]. However, electrospinning of pitches has also been reported [199, 200]. Pitches can also be mixed with PAN to yield a composite of hard and soft CF [201]. The CF obtained from isotropic pitch and mesophase pitch is different in terms of structure, properties and nanotexture [23]. Mesophase pitch already contains small graphitic crystallites and the resulting fibers are high-performance fibers, hence and are produced commercially [194, 202, 203]. CFs from isotropic pitch are of general-purpose grade and have low modulus [203]. Pitch-based fibers are used as an alternative to PAN-based CF in various applications due to its higher stiffness. Apart from that, their electrical properties are utilized in energy storage devices. More information on pitch-based fibers and their applications can be found in the recent reviews by Liu et al. [197] and Daulbayev et al. [204].

Bulk industrial carbon production

Highly oriented pyrolytic graphite

HOPG is a synthetic graphite which is prepared by thermal and/or stress annealing of pyrolytic graphite [5]. Pyrolytic graphite is nothing but multiple layers of graphene deposited by CVD of hydrocarbons. These graphene layers are initially defect-containing and turbostratic (randomly oriented), but they organize themselves in an ABABA fashion with an interlayer spacing of <3.36 nm when heated at very high (typically 2500–3000°C) temperatures as shown in Fig. 5 (pathway A–B). When pyrolytic graphite is subjected to high temperatures and uni-axial compressive stress, the mosaic spread (angle between the tiles of graphite) is reduced. HOPG, however, is not a unique material. It is graded based on the mosaic spread. If the mosaic spread is less than 1°, it is called HOPG. Other methods to obtain HOPG include heat-treatment of polymers such as PVC, anthracene that yield graphitizing carbons [205]. One common application of HOPG is also production of graphene via exfoliation as shown in Fig. 5 (pathway B–C) from HOPG prepared by pathway A–B (Fig. 5). The exfoliation process can be physically, chemically or electrochemically assisted. Physical exfoliation methods use mechanical/ultrasonic forces (sonication) to break the weak van der waals bonds between the individual layers of HOPG and obtain graphene layers [104, 206–208]. Chemical exfoliation of HOPG generates reduced graphene oxide (r-GO) as the final product, by treating HOPG with strong acids (sulfuric/nitric acids) at a temperature slightly higher than the ambient temperature [209]. Electrochemical exfoliation methods involve intercalation of some ions electro-chemically driven in-between the layers of HOPG, leading to mesoscale mechanical exfoliation [210–212]. HOPG is used for a variety of applications including X-ray optics and spectroscopy [213, 214], anode material for Li-ion batteries [215–217] and as a substrate for thin-film deposition [218].

schematic of HOPG formation from CVD graphene and graphene formation from HOPG.
Figure 5:

schematic of HOPG formation from CVD graphene and graphene formation from HOPG.

Glass-like carbon

GC is a type of non-graphitizing carbon [219], that is formed by coking during its carbonization from organic precursors. Most common precursors of this type of carbon are phenolic resins [220] or (poly)-furfuryl alcohols [221]. The precursor resin is first cured/cross-linked and then heated to elevated temperatures at a very slow rate. The resins are heat treated to temperatures as high as 3000°C, to anneal out structural defects [51]. During carbonization, inter-twinning of randomly oriented graphene sheets takes place, giving rise to closed inaccessible pores. GC contains fullerene-like structures that also contribute to its low density [65]. These curved structural units make it difficult for the graphitic planes organize during further heat treatment, hence the value of Lc is always >3.36. The microstructure of this type of carbon has been studied in the past and various models proposed [42, 51, 65, 219], which reveal the short-range ordering among graphitic crystallites and randomly oriented basal planes.

GC is hard and brittle, resistant to chemical attacks and features higher tensile and compressive strength [51]. Many large-scale applications of GC-like chemical reactor linings and laboratory crucibles/substrates utilize its chemical inertness, which makes it impermeable to gases and liquids [222]. Other applications include reference electrodes for electrochemical studies [223], medical implants [224, 225] and molds for glass lenses [226]. However, production of bulk GC still has scope for optimization due to the following reasons: (i) the precursor resins used for production of GC are expensive and the high carbonization temperatures increase the overall production cost, (ii) inevitable weight loss during carbonization, (iii) difficulty in machining GC to close tolerances and (iv) difficulty in obtaining thicker (>5 mm) GC parts without porosity [51]. However, this material is studied extensively in the micro and nano-scale by photo patterning the precursor resins and carbonizing them, to obtain GC micro-nano structures, utilized for various applications, which is discussed in the section ‘Fabrication of carbon-based micro and nano devices.’

Activated carbon

Activated carbons exhibit a surface that can easily adsorb foreign molecules (liquids and gases) owing to the presence of porosity and active chemical functional groups. The gas/liquid molecules are held by weak forces (van der waals and london dispersion forces) [227, 228] that can often be released at higher temperatures or use of a chemical effluent [229]. They are prepared by physical or chemical activation of porous carbons, which are in turn obtained by pyrolysis of natural polymers. Activation process generally increases the fraction of micropores (<2 nm) and the overall surface area of the material as well create some active functional groups on its surface [230]. Porous carbons are non-graphitizing. They experience direct charring during their pyrolysis and contain fractal pore geometries (i.e. the pore sizes repeatedly decrease [231]). During its carbonization, the original skeleton of the precursor material is preserved and these types of carbons exhibit very high porosity (micro/meso/macro pores) and thus, a high surface area [229]. To produce porous carbons, the heat-treatment temperature should not be very high (typically limited to <1000°C), as higher temperatures may lead to closing or annealing of some pores [51]. Common precursors used for obtaining porous carbons include coal, petroleum residues and cellulose-based precursors (coconut shells, rice husk, wood and various biodegradable materials) [51]. Lately, a large number of agricultural and forestry residues have been utilized for the preparation of porous carbons that can be further activated. Some of these are covered in the section ‘Waste treatment via pyrolysis.’

Physical activation is done on porous carbons prepared at low temperatures, which involves heating these carbons at a higher temperature to get rid of pyrolysis by-products (tars), trapped inside the pores, thereby increasing the porosity. Another method of physical activation is to heat these porous carbona in an oxidizing environment [230]. Chemical activation is done on bio-polymers before the carbonization process by treating the precursor with some chemicals (acids/metal carbonates/metal chlorides, etc.) to partially degrade the cellulose. The polymer is then carbonized and the carbon is activated [230]. There are also many other methods of activation of porous carbons that involve combination of both physical and chemical activation processes. Interested readers can refer to the review article by Sevilla et al. [96]. Applications of activated carbons include water purification [232–234]; environmental remediation [235–237]; supercapacitor electrode material [238, 239] and as an adsorbent in food, agriculture and pharmaceutical industries [240–242].

Fabrication of carbon-based micro and nano devices

Carbon-based micro and nano devices can be fabricated using carbon nanomaterials (bottom-up manufacturing) or by directly converting a polymer structure into carbon via pyrolysis (top-down manufacturing). In this section, we will discuss representative examples of micro/nano-scale carbon structures and devices that are fabricated via pyrolysis of pre-patterned polymer structures. Such structures are often first patterned employing lithographic processes such as photolithography [11], X-ray lithography [243] and two-photon lithography [244] on to a silicon substrate, and are subsequently carbonized at temperatures 900° [9]. Another top-down approach that has recently gained popularity is the laser-assisted carbonization of a polymer film [10, 245, 246], which will be subsequently discussed.

Carbonization of lithographically patterned polymers

Lithography is a term used for top-down processes where a polymer film is patterned employing an electromagnetic radiation, or a high energy beam of electrons or ions. The energy of the radiation either degrades or crosslinks the exposed part of the polymer, thus modifying its chemical properties and changing its solubility. The polymers used in lithographic techniques are specifically designed for this purpose. For example, polymers that can be pattered using UV/deep-UV (photolithography) or two back-to-back photons (two-photon lithography) are able to crosslink when exposed to a pre-defined dose of the respective light due to the presence of photo-initiators moieties in their chemical structure. Interestingly, many polymers that are used in photolithography are resins that have a high carbon content and an aromatic backbone. Such polymers can yield a high fraction of solid carbon when they are pyrolyzed. This property has been widely explored for the fabrication of carbon-based devices and has been reported in various articles [7–11, 247, 248].

While converting lithographically patterned resins into carbon, the following points must be taken into consideration: (i) structures shrink due to loss of non-carbon atoms, (ii) resulting carbon is of non-graphitizing type [65, 219] which shows properties similar to commercial GC and (iii) the pyrolysis temperatures are typically limited to 1200°C, due to the fact that silicon substrates cannot withstand temperatures 1400°C (process temperature is kept lower for avoiding thermal stresses and fatigue). The pyrolysis temperature should also not be below 900°C, as that would yield carbon with impurities and poor electrical conductivity. Evidently, flexible polymers cannot be used as the substrate. Figure 6 is a compilation of various carbon-based micro/nano devices produced by carbonization of photo-patterned polymers.

SEM images of inter-digitated carbon electrodes (A, B), the entire device (C), (A–C) reproduced with permission from Mantis et al. [248]; SEM images of sideview of optimized CNG at the edge of an electrode area (D), CNG electrodes with uniform residual bulk carbon layer connecting the CNG, (red arrows) (E), the entire device (F), (D–F), reproduced with permission from Asif et al. [249]; SEM images of suspended GCWs before and after the LCVD process (G), overview of multiple fibers suspended from scaffolds, illustrating how they can be locally coated (bright fibers) or left uncoated (darker fibers) without contaminating the carbon scaffold (H), the entire device (I), (G–I) reproduced with permission from Cisquella-Serra et al. [247]; SEM images of CMN array (J), magnified view of a CMN (K), the entire device (L), (J, K), reproduced with permission and (K) modified from Mishra et al. [250]. CNG, carbon nanograss; GCWs, glassy carbon wires; LCVD, localized CVD; CMN, carbon micro-needle.
Figure 6:

SEM images of inter-digitated carbon electrodes (A, B), the entire device (C), (A–C) reproduced with permission from Mantis et al. [248]; SEM images of sideview of optimized CNG at the edge of an electrode area (D), CNG electrodes with uniform residual bulk carbon layer connecting the CNG, (red arrows) (E), the entire device (F), (D–F), reproduced with permission from Asif et al. [249]; SEM images of suspended GCWs before and after the LCVD process (G), overview of multiple fibers suspended from scaffolds, illustrating how they can be locally coated (bright fibers) or left uncoated (darker fibers) without contaminating the carbon scaffold (H), the entire device (I), (G–I) reproduced with permission from Cisquella-Serra et al. [247]; SEM images of CMN array (J), magnified view of a CMN (K), the entire device (L), (J, K), reproduced with permission and (K) modified from Mishra et al. [250]. CNG, carbon nanograss; GCWs, glassy carbon wires; LCVD, localized CVD; CMN, carbon micro-needle.

Some representative applications of carbon structures fabricated using this process include neural sensing electrodes [11, 244, 249, 251, 252], cell culture substrates compatible with magnetic resonance imaging [8], fabrication of atomic force microscopy (AFM) tips [9, 253], biosensors [254, 255] and various other applications, which are summarized in Table 3.

Table 3:

Summary of carbon electrodes by pyrolysis of patterned polymeric structures (recent research articles from 2018 to 2021)

S. No.Carbon structureProposed/tested applicationFabrication technologyPrecursor polymerRemarks, if anyRef.
1.3D MicroelectrodeNeurotransmitter detectionTwo Photon NanolithographySU-8In-vivo detection of dopamine in Rat brain slices[244]
2.Microelectrode with suspended nanowiresChemiresistive biosensorPhotolithographySU-8DNA immobilization on carbon nanowires[254]
3.MicroelectrodeMRIPhotolithograpySU-8Better MRI compatibility of GC microelectrodes compared with conventional metal electrodes[8]
4.Multilayer electrodeMultiple devicesPhotolithographySU-8 and Sudan III dyed SU-8Sudan III dyed SU-8 was the sacrificial layer[256]
5.MicroelectrodeActivation of GC microelectrodesPhotolithographySU-8Comparative study between electrically and chemically induced activation[63]
6.Microelectrode of CF matsNeural sensorsPhotolithography and RIEPAN, PI, PDMSNeural recording and stimultation of rat brain[257]
7.Microelectrode arraysNeural sensingPhotolithographySU-8Flexible device on polyimide substrate for enhancing brain penetration[258]
8.Microneedle arraysDrug deliveryPhotolithographySU-8Needles tested on mouse skin without breakage[250]
9.MicroelectrodeHep-B antigen sensingPhotolithographySU-8Electrochemical sensing, LOD-1pM[259]
10.3D MicroelectrodesElectrochemical biosensorPhotolithographySU-8Amperometric glucose detection by graphene-oxide functionalized GC microelectrode[255]
11.GC scaffold with suspended nanowiresLocalized CVD of a transition metal oxidePhotolithography, electrospinningSU-8Potential application for gas sensing, catalysis.[247]
12.3D MicroelectrodeNeural sensingPhotolithographySU-8Flexible device on polyimide substrate folded into 3D form in origami fashion[11]
13.Nanograss electrodesDopamine sensingPhotolithography, Maskless RIESU-8Electrochemical sensing of dopamine[249]
14.Graphene electrodeFabrication of multi-layer graphene electrodesPhotolithography, Ni sputteringSU-8Pyrolytic carbon diffused into Ni and precipitates as multi-layer graphene[260]
15.3D microelectrodesInterdigited electrodesPhotolithography
  • SU-8 (bottom layer)

  • mr-DWL (suspended layer)

Multi-step photolithography with two resists to obtain interdigited suspended electrodes[248]
16.MicroelectrodeElectrochemical sensorsphotolithographySU-8CNT/SU-8 derived pyrolytic carbon for sensing of dopamine[252]
S. No.Carbon structureProposed/tested applicationFabrication technologyPrecursor polymerRemarks, if anyRef.
1.3D MicroelectrodeNeurotransmitter detectionTwo Photon NanolithographySU-8In-vivo detection of dopamine in Rat brain slices[244]
2.Microelectrode with suspended nanowiresChemiresistive biosensorPhotolithographySU-8DNA immobilization on carbon nanowires[254]
3.MicroelectrodeMRIPhotolithograpySU-8Better MRI compatibility of GC microelectrodes compared with conventional metal electrodes[8]
4.Multilayer electrodeMultiple devicesPhotolithographySU-8 and Sudan III dyed SU-8Sudan III dyed SU-8 was the sacrificial layer[256]
5.MicroelectrodeActivation of GC microelectrodesPhotolithographySU-8Comparative study between electrically and chemically induced activation[63]
6.Microelectrode of CF matsNeural sensorsPhotolithography and RIEPAN, PI, PDMSNeural recording and stimultation of rat brain[257]
7.Microelectrode arraysNeural sensingPhotolithographySU-8Flexible device on polyimide substrate for enhancing brain penetration[258]
8.Microneedle arraysDrug deliveryPhotolithographySU-8Needles tested on mouse skin without breakage[250]
9.MicroelectrodeHep-B antigen sensingPhotolithographySU-8Electrochemical sensing, LOD-1pM[259]
10.3D MicroelectrodesElectrochemical biosensorPhotolithographySU-8Amperometric glucose detection by graphene-oxide functionalized GC microelectrode[255]
11.GC scaffold with suspended nanowiresLocalized CVD of a transition metal oxidePhotolithography, electrospinningSU-8Potential application for gas sensing, catalysis.[247]
12.3D MicroelectrodeNeural sensingPhotolithographySU-8Flexible device on polyimide substrate folded into 3D form in origami fashion[11]
13.Nanograss electrodesDopamine sensingPhotolithography, Maskless RIESU-8Electrochemical sensing of dopamine[249]
14.Graphene electrodeFabrication of multi-layer graphene electrodesPhotolithography, Ni sputteringSU-8Pyrolytic carbon diffused into Ni and precipitates as multi-layer graphene[260]
15.3D microelectrodesInterdigited electrodesPhotolithography
  • SU-8 (bottom layer)

  • mr-DWL (suspended layer)

Multi-step photolithography with two resists to obtain interdigited suspended electrodes[248]
16.MicroelectrodeElectrochemical sensorsphotolithographySU-8CNT/SU-8 derived pyrolytic carbon for sensing of dopamine[252]
Table 3:

Summary of carbon electrodes by pyrolysis of patterned polymeric structures (recent research articles from 2018 to 2021)

S. No.Carbon structureProposed/tested applicationFabrication technologyPrecursor polymerRemarks, if anyRef.
1.3D MicroelectrodeNeurotransmitter detectionTwo Photon NanolithographySU-8In-vivo detection of dopamine in Rat brain slices[244]
2.Microelectrode with suspended nanowiresChemiresistive biosensorPhotolithographySU-8DNA immobilization on carbon nanowires[254]
3.MicroelectrodeMRIPhotolithograpySU-8Better MRI compatibility of GC microelectrodes compared with conventional metal electrodes[8]
4.Multilayer electrodeMultiple devicesPhotolithographySU-8 and Sudan III dyed SU-8Sudan III dyed SU-8 was the sacrificial layer[256]
5.MicroelectrodeActivation of GC microelectrodesPhotolithographySU-8Comparative study between electrically and chemically induced activation[63]
6.Microelectrode of CF matsNeural sensorsPhotolithography and RIEPAN, PI, PDMSNeural recording and stimultation of rat brain[257]
7.Microelectrode arraysNeural sensingPhotolithographySU-8Flexible device on polyimide substrate for enhancing brain penetration[258]
8.Microneedle arraysDrug deliveryPhotolithographySU-8Needles tested on mouse skin without breakage[250]
9.MicroelectrodeHep-B antigen sensingPhotolithographySU-8Electrochemical sensing, LOD-1pM[259]
10.3D MicroelectrodesElectrochemical biosensorPhotolithographySU-8Amperometric glucose detection by graphene-oxide functionalized GC microelectrode[255]
11.GC scaffold with suspended nanowiresLocalized CVD of a transition metal oxidePhotolithography, electrospinningSU-8Potential application for gas sensing, catalysis.[247]
12.3D MicroelectrodeNeural sensingPhotolithographySU-8Flexible device on polyimide substrate folded into 3D form in origami fashion[11]
13.Nanograss electrodesDopamine sensingPhotolithography, Maskless RIESU-8Electrochemical sensing of dopamine[249]
14.Graphene electrodeFabrication of multi-layer graphene electrodesPhotolithography, Ni sputteringSU-8Pyrolytic carbon diffused into Ni and precipitates as multi-layer graphene[260]
15.3D microelectrodesInterdigited electrodesPhotolithography
  • SU-8 (bottom layer)

  • mr-DWL (suspended layer)

Multi-step photolithography with two resists to obtain interdigited suspended electrodes[248]
16.MicroelectrodeElectrochemical sensorsphotolithographySU-8CNT/SU-8 derived pyrolytic carbon for sensing of dopamine[252]
S. No.Carbon structureProposed/tested applicationFabrication technologyPrecursor polymerRemarks, if anyRef.
1.3D MicroelectrodeNeurotransmitter detectionTwo Photon NanolithographySU-8In-vivo detection of dopamine in Rat brain slices[244]
2.Microelectrode with suspended nanowiresChemiresistive biosensorPhotolithographySU-8DNA immobilization on carbon nanowires[254]
3.MicroelectrodeMRIPhotolithograpySU-8Better MRI compatibility of GC microelectrodes compared with conventional metal electrodes[8]
4.Multilayer electrodeMultiple devicesPhotolithographySU-8 and Sudan III dyed SU-8Sudan III dyed SU-8 was the sacrificial layer[256]
5.MicroelectrodeActivation of GC microelectrodesPhotolithographySU-8Comparative study between electrically and chemically induced activation[63]
6.Microelectrode of CF matsNeural sensorsPhotolithography and RIEPAN, PI, PDMSNeural recording and stimultation of rat brain[257]
7.Microelectrode arraysNeural sensingPhotolithographySU-8Flexible device on polyimide substrate for enhancing brain penetration[258]
8.Microneedle arraysDrug deliveryPhotolithographySU-8Needles tested on mouse skin without breakage[250]
9.MicroelectrodeHep-B antigen sensingPhotolithographySU-8Electrochemical sensing, LOD-1pM[259]
10.3D MicroelectrodesElectrochemical biosensorPhotolithographySU-8Amperometric glucose detection by graphene-oxide functionalized GC microelectrode[255]
11.GC scaffold with suspended nanowiresLocalized CVD of a transition metal oxidePhotolithography, electrospinningSU-8Potential application for gas sensing, catalysis.[247]
12.3D MicroelectrodeNeural sensingPhotolithographySU-8Flexible device on polyimide substrate folded into 3D form in origami fashion[11]
13.Nanograss electrodesDopamine sensingPhotolithography, Maskless RIESU-8Electrochemical sensing of dopamine[249]
14.Graphene electrodeFabrication of multi-layer graphene electrodesPhotolithography, Ni sputteringSU-8Pyrolytic carbon diffused into Ni and precipitates as multi-layer graphene[260]
15.3D microelectrodesInterdigited electrodesPhotolithography
  • SU-8 (bottom layer)

  • mr-DWL (suspended layer)

Multi-step photolithography with two resists to obtain interdigited suspended electrodes[248]
16.MicroelectrodeElectrochemical sensorsphotolithographySU-8CNT/SU-8 derived pyrolytic carbon for sensing of dopamine[252]

Laser-assisted pyrolysis of polymers

A top-down fabrication technique for obtaining polymeric carbon structures is based on conversion of a high carbon containing polymer directly using a laser beam. Laser has been used in the past for production of carbon nanomaterials from thermal decomposition of hydrocarbons [261, 262], where reactants are heated by laser in a closed chamber causing the reactants to de-compose and the aggregates undergo homogeneous nucleation and growth to form hydrogen-rich carbon powders. Carbon-rich polymer films, when irradiated by a laser, undergo thermo-chemical decompositions to yield carbon structures, which can be used in micro/nano device applications. This pyrolysis is a combination of photochemical and photothermal mechanisms [263, 264]. Laser intensity is insufficient for direct bond dissociation of the polymer, but the radiation induces phonons in the material. The vibrational energy of the phonons is released by bond dissociation of the weaker components of the polymer [265]. This leads to material ablation from the surface in the form of bubbles and is expressed as ‘bleaching’ at a fluence is below carbonization threshold. Further increase in fluence leads to an immediate burst of the bubbles, resulting in rapid release of volatile products due to fragmentation of the polymer. Under constant radiation, these fragments become ionized and form a plume (plasma-like discharge). The plume-shield prevents further penetration of the beam into the material, resulting in heat generation at the beam front and adjacent areas resulting in carbonization of the material [266]. Thus, laser-induced carbonization is complete only when the plume has formed (visible as a bright spot by the naked eye).

Laser-induced carbonization has been applied successfully to polyimide [10, 245, 267, 268], parylene-C [269, 270] and polyaramid [246] to yield carbon structures, different from both glassy and activated carbons owing to the fact that this process happens within a short time and the cleavage of chemical bonds is rapid. The heat generated by the laser and the resulting carbon produced depends on the laser parameters (type of laser, laser power, speed and wavelength) along with the pyrolysis environment [10, 267]. The minimum feature size of carbon structures that can be produced by this method depends on the spot radius of the laser [270]. The microstructure of the laser-induced carbon is thoroughly investigated and applied to various applications such as supercapacitors [74, 267], sensors [10, 270, 271], antibacterial coatings [246, 272] and carbon-based composites [152]. Discrepancies in nomenclature of the same material obtained by laser-induced pyrolysis/carbonization of the same polymer are observed in the subsequent literature. For further details on laser-induced carbonization of polymers, interested readers can refer to the review article on laser-induced graphene by Ruquan Ye et al. [273]. Table 4 summarizes the recent examples of fabrication of carbon-based micro-nano devices by laser-assisted pyrolysis of various polymers and their applications.

Table 4:

Carbon patterns by laser-assisted pyrolysis of polymeric substrates (Research from 2012 to 2021)

S. No.Structure/devicePrecursor polymerProposed applicationRemarks, if anyRef.
1.Microelectrode with suspended CFPolyimideFlexible microsupercapacitor deviceLaser-induced graphene fibers (LIGF) formed from laser-induced graphene (LIG) at radiation energy >40 J/m2[267]
2.Porous carbonPolyimideFlexible on-chip micro supercapacitorPorous foam like microstructures by femto second laser[274]
3.MicroelectrodeParylene-CNeural sensingPolymer-metal-polymer electrode with pyrolysed polymer as active site[269]
4.MicroelectrodePolyimideElectrochemical pH sensorPANI/C-PI composite electrode on a flexible substrate[275]
5.Microelectrode arraysPolyimideNeural stimulationIn-vivo cortical microstimulations in rats[268]
6.Graphene-like structuresPolyimideProtection of graphene-based device from liquid erosion
  • Superhydrophobic graphene using a taro leaf template.

  • Anti-sweat and serum adhesion properties

[276]
7.Hierarchical carbon patternsPolyimidepH-based urea sensorsFlexible device electrochemical sensor[10]
8.Carbonized patternsPolyimideStrain sensorsFabricated instrumented latex glove capable of monitoring finger motion in real time[271]
9.MicroelectrodePolyimideMicrosupercapacitorsPower supply unit for on-chip photo-detector[277]
10.Microelectrode arraysParylene CNeural sensingIn-vitro Dopamine detection, in-vivo experiments, a future scope[270]
11.Carbon patternsPolyaramidAnti-bacterial coatingsCu electrodeposited on flexible carbon patterns[246]
12.3D electrodePolyimideLi-ion battery electrodeGraphene transferred from PI substrate to Cu foil by rolling[278]
13.LIG conductive tracesPolyimideFlexible and light-weight heaters90°C temperature achieved at low voltages (6 V–24 V)[279]
14.LIG filmsPolyimideElectrochemical dopamine sensorsGraphene films formed on polyimide by irradiation of IR and UV laser[280]
15.LIG/PDMS/PSPI compositesPDMS and liquid polyimideWearable strain sensorsPDMS and liquid PI mixture spin coated and laser patterned to form a conductive path[281]
16.LIG/MoO2/CC electrodeCarbon cloth coated with MoO2MicrosupercapacitorsCore-shell electrode formed by laser irradiation on carbon cloth coated MoO2[282]
17.LIG/LDPE compositesPolyimideTriboelectric nanogeneratorsComposite formed by roll to roll[152]
18.Graphene maskPolyimideAntibacterial maskRapid bacteria killing by photogenerated heat[272]
S. No.Structure/devicePrecursor polymerProposed applicationRemarks, if anyRef.
1.Microelectrode with suspended CFPolyimideFlexible microsupercapacitor deviceLaser-induced graphene fibers (LIGF) formed from laser-induced graphene (LIG) at radiation energy >40 J/m2[267]
2.Porous carbonPolyimideFlexible on-chip micro supercapacitorPorous foam like microstructures by femto second laser[274]
3.MicroelectrodeParylene-CNeural sensingPolymer-metal-polymer electrode with pyrolysed polymer as active site[269]
4.MicroelectrodePolyimideElectrochemical pH sensorPANI/C-PI composite electrode on a flexible substrate[275]
5.Microelectrode arraysPolyimideNeural stimulationIn-vivo cortical microstimulations in rats[268]
6.Graphene-like structuresPolyimideProtection of graphene-based device from liquid erosion
  • Superhydrophobic graphene using a taro leaf template.

  • Anti-sweat and serum adhesion properties

[276]
7.Hierarchical carbon patternsPolyimidepH-based urea sensorsFlexible device electrochemical sensor[10]
8.Carbonized patternsPolyimideStrain sensorsFabricated instrumented latex glove capable of monitoring finger motion in real time[271]
9.MicroelectrodePolyimideMicrosupercapacitorsPower supply unit for on-chip photo-detector[277]
10.Microelectrode arraysParylene CNeural sensingIn-vitro Dopamine detection, in-vivo experiments, a future scope[270]
11.Carbon patternsPolyaramidAnti-bacterial coatingsCu electrodeposited on flexible carbon patterns[246]
12.3D electrodePolyimideLi-ion battery electrodeGraphene transferred from PI substrate to Cu foil by rolling[278]
13.LIG conductive tracesPolyimideFlexible and light-weight heaters90°C temperature achieved at low voltages (6 V–24 V)[279]
14.LIG filmsPolyimideElectrochemical dopamine sensorsGraphene films formed on polyimide by irradiation of IR and UV laser[280]
15.LIG/PDMS/PSPI compositesPDMS and liquid polyimideWearable strain sensorsPDMS and liquid PI mixture spin coated and laser patterned to form a conductive path[281]
16.LIG/MoO2/CC electrodeCarbon cloth coated with MoO2MicrosupercapacitorsCore-shell electrode formed by laser irradiation on carbon cloth coated MoO2[282]
17.LIG/LDPE compositesPolyimideTriboelectric nanogeneratorsComposite formed by roll to roll[152]
18.Graphene maskPolyimideAntibacterial maskRapid bacteria killing by photogenerated heat[272]
Table 4:

Carbon patterns by laser-assisted pyrolysis of polymeric substrates (Research from 2012 to 2021)

S. No.Structure/devicePrecursor polymerProposed applicationRemarks, if anyRef.
1.Microelectrode with suspended CFPolyimideFlexible microsupercapacitor deviceLaser-induced graphene fibers (LIGF) formed from laser-induced graphene (LIG) at radiation energy >40 J/m2[267]
2.Porous carbonPolyimideFlexible on-chip micro supercapacitorPorous foam like microstructures by femto second laser[274]
3.MicroelectrodeParylene-CNeural sensingPolymer-metal-polymer electrode with pyrolysed polymer as active site[269]
4.MicroelectrodePolyimideElectrochemical pH sensorPANI/C-PI composite electrode on a flexible substrate[275]
5.Microelectrode arraysPolyimideNeural stimulationIn-vivo cortical microstimulations in rats[268]
6.Graphene-like structuresPolyimideProtection of graphene-based device from liquid erosion
  • Superhydrophobic graphene using a taro leaf template.

  • Anti-sweat and serum adhesion properties

[276]
7.Hierarchical carbon patternsPolyimidepH-based urea sensorsFlexible device electrochemical sensor[10]
8.Carbonized patternsPolyimideStrain sensorsFabricated instrumented latex glove capable of monitoring finger motion in real time[271]
9.MicroelectrodePolyimideMicrosupercapacitorsPower supply unit for on-chip photo-detector[277]
10.Microelectrode arraysParylene CNeural sensingIn-vitro Dopamine detection, in-vivo experiments, a future scope[270]
11.Carbon patternsPolyaramidAnti-bacterial coatingsCu electrodeposited on flexible carbon patterns[246]
12.3D electrodePolyimideLi-ion battery electrodeGraphene transferred from PI substrate to Cu foil by rolling[278]
13.LIG conductive tracesPolyimideFlexible and light-weight heaters90°C temperature achieved at low voltages (6 V–24 V)[279]
14.LIG filmsPolyimideElectrochemical dopamine sensorsGraphene films formed on polyimide by irradiation of IR and UV laser[280]
15.LIG/PDMS/PSPI compositesPDMS and liquid polyimideWearable strain sensorsPDMS and liquid PI mixture spin coated and laser patterned to form a conductive path[281]
16.LIG/MoO2/CC electrodeCarbon cloth coated with MoO2MicrosupercapacitorsCore-shell electrode formed by laser irradiation on carbon cloth coated MoO2[282]
17.LIG/LDPE compositesPolyimideTriboelectric nanogeneratorsComposite formed by roll to roll[152]
18.Graphene maskPolyimideAntibacterial maskRapid bacteria killing by photogenerated heat[272]
S. No.Structure/devicePrecursor polymerProposed applicationRemarks, if anyRef.
1.Microelectrode with suspended CFPolyimideFlexible microsupercapacitor deviceLaser-induced graphene fibers (LIGF) formed from laser-induced graphene (LIG) at radiation energy >40 J/m2[267]
2.Porous carbonPolyimideFlexible on-chip micro supercapacitorPorous foam like microstructures by femto second laser[274]
3.MicroelectrodeParylene-CNeural sensingPolymer-metal-polymer electrode with pyrolysed polymer as active site[269]
4.MicroelectrodePolyimideElectrochemical pH sensorPANI/C-PI composite electrode on a flexible substrate[275]
5.Microelectrode arraysPolyimideNeural stimulationIn-vivo cortical microstimulations in rats[268]
6.Graphene-like structuresPolyimideProtection of graphene-based device from liquid erosion
  • Superhydrophobic graphene using a taro leaf template.

  • Anti-sweat and serum adhesion properties

[276]
7.Hierarchical carbon patternsPolyimidepH-based urea sensorsFlexible device electrochemical sensor[10]
8.Carbonized patternsPolyimideStrain sensorsFabricated instrumented latex glove capable of monitoring finger motion in real time[271]
9.MicroelectrodePolyimideMicrosupercapacitorsPower supply unit for on-chip photo-detector[277]
10.Microelectrode arraysParylene CNeural sensingIn-vitro Dopamine detection, in-vivo experiments, a future scope[270]
11.Carbon patternsPolyaramidAnti-bacterial coatingsCu electrodeposited on flexible carbon patterns[246]
12.3D electrodePolyimideLi-ion battery electrodeGraphene transferred from PI substrate to Cu foil by rolling[278]
13.LIG conductive tracesPolyimideFlexible and light-weight heaters90°C temperature achieved at low voltages (6 V–24 V)[279]
14.LIG filmsPolyimideElectrochemical dopamine sensorsGraphene films formed on polyimide by irradiation of IR and UV laser[280]
15.LIG/PDMS/PSPI compositesPDMS and liquid polyimideWearable strain sensorsPDMS and liquid PI mixture spin coated and laser patterned to form a conductive path[281]
16.LIG/MoO2/CC electrodeCarbon cloth coated with MoO2MicrosupercapacitorsCore-shell electrode formed by laser irradiation on carbon cloth coated MoO2[282]
17.LIG/LDPE compositesPolyimideTriboelectric nanogeneratorsComposite formed by roll to roll[152]
18.Graphene maskPolyimideAntibacterial maskRapid bacteria killing by photogenerated heat[272]

Analytical pyrolysis

Pyrolysis induces fragmentation in large hydrocarbon molecules without any foreign chemical reactions such as oxidation. This characteristic turns out to be extremely useful for the analysis of trace amounts of invaluable samples, such as the organic matter found in the fossils [14]. The analysis of fossil samples is essential for understanding their origin, age and formation mechanism. MS is one of the primary techniques used for the analysis of fossils, which is based on the principle of analyzing the mass of the various fragments of the molecule.

By evaluating this fragmentation mechanism one can detect the original structure of the initial molecule(s) [98]. Importantly, the sample quantity cannot be increased and needless to say, no amount of sample can be wasted for analytical purposes, hence pyrolysis occurs directly at the ion source to avoid loss of by-products. Pyrolysis MS (Py-MS), however, has one disadvantage that the pyrolytic fragmentation of the molecule is performed in the same chamber of the ion source. This results in contamination of the ion source, affecting long-term reproducibility of mass spectra lines [67]. Py-MS is therefore often combined with GC to form a set of techniques known as Py-GC–MS [283]. Py-GC–MS process entails the integration of pyrolyzing unit (Py), GC system and MS together by connecting the pyrolysis unit to the injector port of a gas chromatograph such that pyrolysis by-products (pyrolysates) are chromatographically separated through fused silica capillary columns by inert gas flow, followed by ionization of the products to obtain a mass spectra which is then analyzed with the help of mass spectra libraries [98, 284]. Depending upon the sample availability and its possible chemical nature, pyrolysis may be performed using ovens, lasers or by utilizing a filament that can be inductively heated to provide the desired temperatures [14]. Thus, pyrolysis may be used as a form of sample pre-treatment for analysis of complex organic materials with unknown structures [285], for example, forensic samples [14, 286, 287], humic materials [16], geopolymers [286], environmental samples [288–290], biological molecules (proteins, peptides and nucleotides) [291] and various other biochemically important polymers as well as some polymers of non-biological origin [64, 67]. A few applications of analytical pyrolysis for analysis of polymers, fossils, archaeological remains and other complex materials are listed in Table 5.

Table 5:

Applications of analytical pyrolysis methods for analysis of various complex materials

S. No.Analytical techniquePyrolysis parametersApplicationRef.
1.Pyrolysis-fast GCPyrolysis temperature; 700°C, pyrolysis time; 20 sAnalysis of synthetic polymers[292]
2.Pyrolysis-GCPyrolysis temperature; 820–840°CArt and archaeology (Review)[293]
3.Pyrolysis-GCPyrolysis temperature range; 100–700°CInvestigation of humic substances in soil[16]
4.Laser pyrolysis-MSPyrolysis temperatures range; 200°C and 350°CCharacterization of biomass char[15]
5.Pyrolysis-GC, Pyrolysis-MSPyrolysis temperature range; 200–1300°C different temperature range for different studiesBiomedical studies (Fingerprinting carbohydrates, nucleic acids, bacteria, fungi, etc.) (Review)[291]
6.Pyrolysis-GC/MS
  • Pyrolysis temperature; 700°C

  • Pyrolysis time; 10 s

Characterization of old inks from books dated 1540 and 1778[294]
7.Pyrolysis-GC/MS
  • Pyrolysis temperature; 770°C

  • Pyrolysis time; 10 s

Study composition of weathered building materials[295]
8.Pyrolysis-GC/MS
  • Pyrolysis temperature range;

  • 300–800°C (furnace pyrolyzer)

  • 600–800°C (filament pyrolyzer)

Determinations of structural composition of organic matter in sedimentary rocks (kerogen)[14]
9.Pyrolysis-GC/MSPyrolysis temperature range; 50–750°CRapid screening of contaminants in environmental samples[288]
10.Pyrolysis-GC/MSPyrolysis temperature; 610°CForensic studies related to petroleum and crude oil spills[286]
11.Pyrolysis-GC/MSPyrolysis temperature; 800°CFast identification of polymer additives (ABS polymer from electronic industry)[296]
12.Pyrolysis-GC/MSPyrolysis temperature; 700°CIdentification of microplastics in marine litter[289]
13.Pyrolysis-GC/MSPyrolysis temperature; 700°C, 20°C/minCharacterization of lignin extracted from various archaeological sites of the world (Poland, Norway, Italy, spain, France)[287]
14.Pyrolysis-GC/MSPyrolysis temperature; 500°C (unfailed sample), 700°C (unfailed sample)Identification of organic compounds in chemical, rubber, and automotive industry for failure analysis[297]
S. No.Analytical techniquePyrolysis parametersApplicationRef.
1.Pyrolysis-fast GCPyrolysis temperature; 700°C, pyrolysis time; 20 sAnalysis of synthetic polymers[292]
2.Pyrolysis-GCPyrolysis temperature; 820–840°CArt and archaeology (Review)[293]
3.Pyrolysis-GCPyrolysis temperature range; 100–700°CInvestigation of humic substances in soil[16]
4.Laser pyrolysis-MSPyrolysis temperatures range; 200°C and 350°CCharacterization of biomass char[15]
5.Pyrolysis-GC, Pyrolysis-MSPyrolysis temperature range; 200–1300°C different temperature range for different studiesBiomedical studies (Fingerprinting carbohydrates, nucleic acids, bacteria, fungi, etc.) (Review)[291]
6.Pyrolysis-GC/MS
  • Pyrolysis temperature; 700°C

  • Pyrolysis time; 10 s

Characterization of old inks from books dated 1540 and 1778[294]
7.Pyrolysis-GC/MS
  • Pyrolysis temperature; 770°C

  • Pyrolysis time; 10 s

Study composition of weathered building materials[295]
8.Pyrolysis-GC/MS
  • Pyrolysis temperature range;

  • 300–800°C (furnace pyrolyzer)

  • 600–800°C (filament pyrolyzer)

Determinations of structural composition of organic matter in sedimentary rocks (kerogen)[14]
9.Pyrolysis-GC/MSPyrolysis temperature range; 50–750°CRapid screening of contaminants in environmental samples[288]
10.Pyrolysis-GC/MSPyrolysis temperature; 610°CForensic studies related to petroleum and crude oil spills[286]
11.Pyrolysis-GC/MSPyrolysis temperature; 800°CFast identification of polymer additives (ABS polymer from electronic industry)[296]
12.Pyrolysis-GC/MSPyrolysis temperature; 700°CIdentification of microplastics in marine litter[289]
13.Pyrolysis-GC/MSPyrolysis temperature; 700°C, 20°C/minCharacterization of lignin extracted from various archaeological sites of the world (Poland, Norway, Italy, spain, France)[287]
14.Pyrolysis-GC/MSPyrolysis temperature; 500°C (unfailed sample), 700°C (unfailed sample)Identification of organic compounds in chemical, rubber, and automotive industry for failure analysis[297]
Table 5:

Applications of analytical pyrolysis methods for analysis of various complex materials

S. No.Analytical techniquePyrolysis parametersApplicationRef.
1.Pyrolysis-fast GCPyrolysis temperature; 700°C, pyrolysis time; 20 sAnalysis of synthetic polymers[292]
2.Pyrolysis-GCPyrolysis temperature; 820–840°CArt and archaeology (Review)[293]
3.Pyrolysis-GCPyrolysis temperature range; 100–700°CInvestigation of humic substances in soil[16]
4.Laser pyrolysis-MSPyrolysis temperatures range; 200°C and 350°CCharacterization of biomass char[15]
5.Pyrolysis-GC, Pyrolysis-MSPyrolysis temperature range; 200–1300°C different temperature range for different studiesBiomedical studies (Fingerprinting carbohydrates, nucleic acids, bacteria, fungi, etc.) (Review)[291]
6.Pyrolysis-GC/MS
  • Pyrolysis temperature; 700°C

  • Pyrolysis time; 10 s

Characterization of old inks from books dated 1540 and 1778[294]
7.Pyrolysis-GC/MS
  • Pyrolysis temperature; 770°C

  • Pyrolysis time; 10 s

Study composition of weathered building materials[295]
8.Pyrolysis-GC/MS
  • Pyrolysis temperature range;

  • 300–800°C (furnace pyrolyzer)

  • 600–800°C (filament pyrolyzer)

Determinations of structural composition of organic matter in sedimentary rocks (kerogen)[14]
9.Pyrolysis-GC/MSPyrolysis temperature range; 50–750°CRapid screening of contaminants in environmental samples[288]
10.Pyrolysis-GC/MSPyrolysis temperature; 610°CForensic studies related to petroleum and crude oil spills[286]
11.Pyrolysis-GC/MSPyrolysis temperature; 800°CFast identification of polymer additives (ABS polymer from electronic industry)[296]
12.Pyrolysis-GC/MSPyrolysis temperature; 700°CIdentification of microplastics in marine litter[289]
13.Pyrolysis-GC/MSPyrolysis temperature; 700°C, 20°C/minCharacterization of lignin extracted from various archaeological sites of the world (Poland, Norway, Italy, spain, France)[287]
14.Pyrolysis-GC/MSPyrolysis temperature; 500°C (unfailed sample), 700°C (unfailed sample)Identification of organic compounds in chemical, rubber, and automotive industry for failure analysis[297]
S. No.Analytical techniquePyrolysis parametersApplicationRef.
1.Pyrolysis-fast GCPyrolysis temperature; 700°C, pyrolysis time; 20 sAnalysis of synthetic polymers[292]
2.Pyrolysis-GCPyrolysis temperature; 820–840°CArt and archaeology (Review)[293]
3.Pyrolysis-GCPyrolysis temperature range; 100–700°CInvestigation of humic substances in soil[16]
4.Laser pyrolysis-MSPyrolysis temperatures range; 200°C and 350°CCharacterization of biomass char[15]
5.Pyrolysis-GC, Pyrolysis-MSPyrolysis temperature range; 200–1300°C different temperature range for different studiesBiomedical studies (Fingerprinting carbohydrates, nucleic acids, bacteria, fungi, etc.) (Review)[291]
6.Pyrolysis-GC/MS
  • Pyrolysis temperature; 700°C

  • Pyrolysis time; 10 s

Characterization of old inks from books dated 1540 and 1778[294]
7.Pyrolysis-GC/MS
  • Pyrolysis temperature; 770°C

  • Pyrolysis time; 10 s

Study composition of weathered building materials[295]
8.Pyrolysis-GC/MS
  • Pyrolysis temperature range;

  • 300–800°C (furnace pyrolyzer)

  • 600–800°C (filament pyrolyzer)

Determinations of structural composition of organic matter in sedimentary rocks (kerogen)[14]
9.Pyrolysis-GC/MSPyrolysis temperature range; 50–750°CRapid screening of contaminants in environmental samples[288]
10.Pyrolysis-GC/MSPyrolysis temperature; 610°CForensic studies related to petroleum and crude oil spills[286]
11.Pyrolysis-GC/MSPyrolysis temperature; 800°CFast identification of polymer additives (ABS polymer from electronic industry)[296]
12.Pyrolysis-GC/MSPyrolysis temperature; 700°CIdentification of microplastics in marine litter[289]
13.Pyrolysis-GC/MSPyrolysis temperature; 700°C, 20°C/minCharacterization of lignin extracted from various archaeological sites of the world (Poland, Norway, Italy, spain, France)[287]
14.Pyrolysis-GC/MSPyrolysis temperature; 500°C (unfailed sample), 700°C (unfailed sample)Identification of organic compounds in chemical, rubber, and automotive industry for failure analysis[297]

Waste treatment via pyrolysis

Human, animal and plant waste contains a significant fraction of organic matter. While direct burning or combustion of waste polymers is hazardous to the environment, pyrolysis can lead to their safe disposal. The tars, gases and solid carbon residues (often called chars or biochars due to their low purity) produced during the pyrolysis of waste can also be utilized in various applications. As a result, one of the most widely studied applications of the pyrolysis process in the industry and academia at present is the treatment of waste. Here, the process is stopped at the end of the pyrolysis stage itself (generally before 700°C). The desired products are oils (tarry hydrocarbons produced by fragmentation of waste polymers) and synthetic gas (mixture of light hydrocarbons). Similar to other pyrolytic decomposition processes, waste materials which contain organic materials (biodegradable and non-biodegradable) are heated to produce the desired products. Notably, solid carbon fractions obtained at low temperatures (below 700°C) contain a significant amount of impurities and they can only be used for low-cost applications such as soil quality enhancement, oil spillage adsorbents and other industrial cleaning agents [298–300]. The quality improvement of such carbons is being extensively investigated. In the recent, past several waste-derived carbon materials have been used for advanced applications such as electrode fabrication. It is important to understand that increase in the solid carbon fraction may reduce the oil/gas production. Moreover, higher pyrolysis temperatures increase the cost of the overall process, which may not always be feasible when it comes to large-scale waste treatment. As a result, one needs to evaluate the final products prior to designing the process parameters. Various products of waste pyrolysis along with their calorific value are listed in Table 6.

Table 6:

Preparation and calorific values of the common pyrolysis products of the current waste pyrolysis facilities

S. No.ProductsCalorific valuePyrolysis conditionsRemarksRef.
1Syngas13–14 MJ/Nm3
  • Final temperature: 900°C

  • Ramp rate: 10°C/min

Produced in the range of 47–67 mol%. Production strongly depends on temperature, heating rate, and waste constituents.[58]
2Pyrolysis Oil40 MJ/kg
  • Final temperature: 440°C Ramp rate: 20°C/min,

  • Atmosphere: Nitrogen

  • Residence time: 30 min

Sold as an alternative fuel. Higher calorific value for plastic-derived oils.[12] [13]
3Char34 MJ/kg
  • Temperature: 300°C

  • Atmosphere: Nitrogen,

  • Residence time: 30 min

  • May contain heavy metals and hazardous elements like S, Cl, and Ni.

  • Composition differs for different precursors.

[12, 301, 302]
S. No.ProductsCalorific valuePyrolysis conditionsRemarksRef.
1Syngas13–14 MJ/Nm3
  • Final temperature: 900°C

  • Ramp rate: 10°C/min

Produced in the range of 47–67 mol%. Production strongly depends on temperature, heating rate, and waste constituents.[58]
2Pyrolysis Oil40 MJ/kg
  • Final temperature: 440°C Ramp rate: 20°C/min,

  • Atmosphere: Nitrogen

  • Residence time: 30 min

Sold as an alternative fuel. Higher calorific value for plastic-derived oils.[12] [13]
3Char34 MJ/kg
  • Temperature: 300°C

  • Atmosphere: Nitrogen,

  • Residence time: 30 min

  • May contain heavy metals and hazardous elements like S, Cl, and Ni.

  • Composition differs for different precursors.

[12, 301, 302]
Table 6:

Preparation and calorific values of the common pyrolysis products of the current waste pyrolysis facilities

S. No.ProductsCalorific valuePyrolysis conditionsRemarksRef.
1Syngas13–14 MJ/Nm3
  • Final temperature: 900°C

  • Ramp rate: 10°C/min

Produced in the range of 47–67 mol%. Production strongly depends on temperature, heating rate, and waste constituents.[58]
2Pyrolysis Oil40 MJ/kg
  • Final temperature: 440°C Ramp rate: 20°C/min,

  • Atmosphere: Nitrogen

  • Residence time: 30 min

Sold as an alternative fuel. Higher calorific value for plastic-derived oils.[12] [13]
3Char34 MJ/kg
  • Temperature: 300°C

  • Atmosphere: Nitrogen,

  • Residence time: 30 min

  • May contain heavy metals and hazardous elements like S, Cl, and Ni.

  • Composition differs for different precursors.

[12, 301, 302]
S. No.ProductsCalorific valuePyrolysis conditionsRemarksRef.
1Syngas13–14 MJ/Nm3
  • Final temperature: 900°C

  • Ramp rate: 10°C/min

Produced in the range of 47–67 mol%. Production strongly depends on temperature, heating rate, and waste constituents.[58]
2Pyrolysis Oil40 MJ/kg
  • Final temperature: 440°C Ramp rate: 20°C/min,

  • Atmosphere: Nitrogen

  • Residence time: 30 min

Sold as an alternative fuel. Higher calorific value for plastic-derived oils.[12] [13]
3Char34 MJ/kg
  • Temperature: 300°C

  • Atmosphere: Nitrogen,

  • Residence time: 30 min

  • May contain heavy metals and hazardous elements like S, Cl, and Ni.

  • Composition differs for different precursors.

[12, 301, 302]

Pyrolytic synthetic (syn) gas

The composition of the pyrolytic gas is strongly dependent on the pyrolysis temperature and feed-stock. Slow pyrolysis of biomass waste such as wood, garden waste and food residue at low temperatures (below 400°C) produces small amounts of gas, which is rich in CO2, CO and light hydrocarbons. The yields of gas at these conditions usually do not exceed 30 wt.% of pyrolysis products. On increasing the temperature there is an increase in gas yields, because of the secondary reactions and partial char decomposition. The calorific value of gas from slow pyrolysis is around 10–15 MJ/Nm3 and varies with temperature and heating rate [303]. Fast pyrolysis of biomass produces gas with a calorific value of around 14 MJ/Nm3. On the other hand, higher temperatures (above 700°C), especially when pyrolysis is combined with gasification, produces syngas, which contains more hydrogen and carbon monoxide. In this case, syngas is the main product of the process. The pyrolysis of plastics produces pyrolytic gas, of which the major components are hydrogen and light hydrocarbons: methane, ethane, ethene, propane, propene and butane. This gas has a significant calorific value, for example, a heating value of gas from PP and PE varied between 42 and 50 MJ/kg [304]. Similar properties characterized the gas from the pyrolysis of tyres or other artificial products like textiles. In turn, co-pyrolysis of polymers and biomass leads to a higher production of CO and CO2 especially at lower temperatures. Finally, the pyrogas from MSW consists of CO2, CO, hydrogen, methane and other light hydrocarbons with an average heating value of around 15 MJ/Nm3, which increases with increasing temperature [305]. The most suitable demand on pyrogas is its use as a source of the energy required for the pyrolysis process itself. However, the exhaust gas has to be controlled. Pyrogas from tyres contains a relatively high concentration of H2S, which can be oxidized to SO2 [306]. PVC pyrolysis produces huge amounts of HCl [307] whereas waste food processing could be a source of dangerous nitrogen compounds [308]. Usually the precise composition of waste is unknown, thus some unwanted compounds can appear in pyrogas. Therefore, emission control units and gas cleaning devices should be used and it does not matter whether the gas will be combusted or not.

Pyrolytic oil

Pyrolytic oil offers more opportunities for use than syngas, but the composition of the liquid product from pyrolysis may differ radically depending on the composition of the feedstock and the process parameters. Pyrolytic oils derived from biomass consist mainly of the following compounds: acids, ketones, aldehydes, sugars, alcohols, phenols and their derivatives, furans and other mixed oxygenates. Phenolic compounds are mostly present in high concentrations (up to 50 wt.%), consisting of relatively small amounts of cresols, xylenols, phenol, eugenol and much larger quantities of alkylated (poly-) phenols [309]. It can be used for the production of heat, electricity, synthetic gas or chemicals. The highest yields of oil are gained between 500°C and 600°C. Pyrolytic oil from biomass has calorific values of around 15–20 MJ/kg, on the other hand, pyrolytic oil from plastics has a higher calorific value, about 30–45 MJ/kg, depending on the precursor polymer. Ahmad et al. [13] compared the oils from the pyrolysis of PP and HDPE with gasoline and diesel via physical properties such as viscosity, the research octane number and the motor octane number, as given in Table 7. Pour point, flash point or diesel index could be a good indication of pyrolytic oil quality as a fuel [13, 71]. The calorific value of oils from mixed plastic waste could be estimated at 40 MJ/kg [310].

Table 7:

Comparison of pyrolytic oil from some polymers with standard liquid fuels, reproduced from Ahmad et al. [13]

PropertiesHDPEPPGasolineDiesel
Heating value (MJ/kg)40.540.842.543.0
Viscosity at 40°C (mm2/s)5.084.091.171.9–4.1
Density at 15° (g/cm3)0.890.860.7800.870
Research octane number85.387.681–85
Motor octane number95.397.891–95
Pour point596
Flash point48304252
Diesel index31.0534.3540
PropertiesHDPEPPGasolineDiesel
Heating value (MJ/kg)40.540.842.543.0
Viscosity at 40°C (mm2/s)5.084.091.171.9–4.1
Density at 15° (g/cm3)0.890.860.7800.870
Research octane number85.387.681–85
Motor octane number95.397.891–95
Pour point596
Flash point48304252
Diesel index31.0534.3540
Table 7:

Comparison of pyrolytic oil from some polymers with standard liquid fuels, reproduced from Ahmad et al. [13]

PropertiesHDPEPPGasolineDiesel
Heating value (MJ/kg)40.540.842.543.0
Viscosity at 40°C (mm2/s)5.084.091.171.9–4.1
Density at 15° (g/cm3)0.890.860.7800.870
Research octane number85.387.681–85
Motor octane number95.397.891–95
Pour point596
Flash point48304252
Diesel index31.0534.3540
PropertiesHDPEPPGasolineDiesel
Heating value (MJ/kg)40.540.842.543.0
Viscosity at 40°C (mm2/s)5.084.091.171.9–4.1
Density at 15° (g/cm3)0.890.860.7800.870
Research octane number85.387.681–85
Motor octane number95.397.891–95
Pour point596
Flash point48304252
Diesel index31.0534.3540

Pyrolytic char

Currently, pyrolysis conditions are generally optimized in order to maximize the liquid and gas products. Besides these two, a solid fraction named as pyrolytic char is also produced. Char mainly is carbon-rich matrix containing almost all the inorganic compounds present in the wastes with a significant amount of condensed by-products of the pyrolysis process [311]. Chars are generally porous and its porosity depends upon precursor waste [7]. The calorific value of char obtained from pyrolysis of waste (mixture of biodegradable and non-biodegradable) is approximately 34 MJ/kg [302], which is comparable with coal. However, despite all the separation techniques before pyrolysis, some heavy metals and other hazardous elements, like S, Cl and Ni, get retained in the solid products. Therefore, it becomes equally important to characterize chars so as to assess their impact on the environment and humans. In general, this product can be combusted to provide energy for the pyrolysis process or other applications as listed in Table 8.

Table 8:

Applications of waste-derived pyrolytic carbon

S. NoProductsPrecursor materialRemarks (if any)Ref.
1.Battery electrodeBiomass (various)Review article[312]
2.Rice huskLithium ion batteries[313]
3.BambooLithium ion batteries[314]
4.shaddock peelSodium ion batteries[315]
5.Coffee groundsSodium ion batteries[316]
6.Supercapacitor electrodeRice huskRHC: KOH = 1:5 by mass was used for activation[317]
7.CarrotZnCl2 as activation agent[318]
8.Biomass (various)Review article[319]
9.Coconut shell[320]
10.Tobacco[321]
11.Tamarind fruit shellActivation of char was done by treating the precursor with KOH[322]
12.Dye sensitized solar panel (counter electrode)Filter paper facial tissue[323]
13.Fish wastePt-free counter electrode[324]
14.Coconut shellAnthocyanin dye extracted from pomegranate juice[325]
15.Anchovy[326]
16.Water filtration or adsorbentsBiomass (various)Review article[327]
17.Nutshells (Almond, English Walnut, Pecan)[328]
18.Apple pulpAdsorption of lead and zinc[329]
19.Fertilizer wasteHeavy metal removal from fixed bed reactor[330]
20.Chickpea[331]
21.Municipal organic solid waste[332]
22.Coconut button[333]
23.Municipal sewage sludge[334]
24.Human hairSensor for dopamine and ascor-bic acid[335]
25.Polyethylene terephthalate (PET) bottlesDetection of carbofuran phenol[336]
26.AmlaSensor for ascorbic acid, dopamine, uric acid and nitrite[337]
27.Onion peelSensor for progesterone[338]
28.Biomass (various)Review article[339]
29.Tetra pak wasteMercury adsorption from water[340]
30.CF manufacturingCotton[341]
31.Prepreg fibersPrepreg is ‘pre-impregnated’ composite fibers[342]
32.Prepreg fibers70% strength when compared with new fibers[343]
33.Filler material for fiberglass/epoxy compositesMetallized food packaging plastic waste0.75 wt.% of char particles improved the modulus of elasticity of panels by approximately 22%, compared with a pure sample.[344]
34.Hybrid fillers for cement industryTextile wasteChar particles (0.05 wt.%) was used as a single filler and hybrid fillers (CNTs/CB and graphene/CB: 50/50) to enhance the properties of cement paste[345]
S. NoProductsPrecursor materialRemarks (if any)Ref.
1.Battery electrodeBiomass (various)Review article[312]
2.Rice huskLithium ion batteries[313]
3.BambooLithium ion batteries[314]
4.shaddock peelSodium ion batteries[315]
5.Coffee groundsSodium ion batteries[316]
6.Supercapacitor electrodeRice huskRHC: KOH = 1:5 by mass was used for activation[317]
7.CarrotZnCl2 as activation agent[318]
8.Biomass (various)Review article[319]
9.Coconut shell[320]
10.Tobacco[321]
11.Tamarind fruit shellActivation of char was done by treating the precursor with KOH[322]
12.Dye sensitized solar panel (counter electrode)Filter paper facial tissue[323]
13.Fish wastePt-free counter electrode[324]
14.Coconut shellAnthocyanin dye extracted from pomegranate juice[325]
15.Anchovy[326]
16.Water filtration or adsorbentsBiomass (various)Review article[327]
17.Nutshells (Almond, English Walnut, Pecan)[328]
18.Apple pulpAdsorption of lead and zinc[329]
19.Fertilizer wasteHeavy metal removal from fixed bed reactor[330]
20.Chickpea[331]
21.Municipal organic solid waste[332]
22.Coconut button[333]
23.Municipal sewage sludge[334]
24.Human hairSensor for dopamine and ascor-bic acid[335]
25.Polyethylene terephthalate (PET) bottlesDetection of carbofuran phenol[336]
26.AmlaSensor for ascorbic acid, dopamine, uric acid and nitrite[337]
27.Onion peelSensor for progesterone[338]
28.Biomass (various)Review article[339]
29.Tetra pak wasteMercury adsorption from water[340]
30.CF manufacturingCotton[341]
31.Prepreg fibersPrepreg is ‘pre-impregnated’ composite fibers[342]
32.Prepreg fibers70% strength when compared with new fibers[343]
33.Filler material for fiberglass/epoxy compositesMetallized food packaging plastic waste0.75 wt.% of char particles improved the modulus of elasticity of panels by approximately 22%, compared with a pure sample.[344]
34.Hybrid fillers for cement industryTextile wasteChar particles (0.05 wt.%) was used as a single filler and hybrid fillers (CNTs/CB and graphene/CB: 50/50) to enhance the properties of cement paste[345]
Table 8:

Applications of waste-derived pyrolytic carbon

S. NoProductsPrecursor materialRemarks (if any)Ref.
1.Battery electrodeBiomass (various)Review article[312]
2.Rice huskLithium ion batteries[313]
3.BambooLithium ion batteries[314]
4.shaddock peelSodium ion batteries[315]
5.Coffee groundsSodium ion batteries[316]
6.Supercapacitor electrodeRice huskRHC: KOH = 1:5 by mass was used for activation[317]
7.CarrotZnCl2 as activation agent[318]
8.Biomass (various)Review article[319]
9.Coconut shell[320]
10.Tobacco[321]
11.Tamarind fruit shellActivation of char was done by treating the precursor with KOH[322]
12.Dye sensitized solar panel (counter electrode)Filter paper facial tissue[323]
13.Fish wastePt-free counter electrode[324]
14.Coconut shellAnthocyanin dye extracted from pomegranate juice[325]
15.Anchovy[326]
16.Water filtration or adsorbentsBiomass (various)Review article[327]
17.Nutshells (Almond, English Walnut, Pecan)[328]
18.Apple pulpAdsorption of lead and zinc[329]
19.Fertilizer wasteHeavy metal removal from fixed bed reactor[330]
20.Chickpea[331]
21.Municipal organic solid waste[332]
22.Coconut button[333]
23.Municipal sewage sludge[334]
24.Human hairSensor for dopamine and ascor-bic acid[335]
25.Polyethylene terephthalate (PET) bottlesDetection of carbofuran phenol[336]
26.AmlaSensor for ascorbic acid, dopamine, uric acid and nitrite[337]
27.Onion peelSensor for progesterone[338]
28.Biomass (various)Review article[339]
29.Tetra pak wasteMercury adsorption from water[340]
30.CF manufacturingCotton[341]
31.Prepreg fibersPrepreg is ‘pre-impregnated’ composite fibers[342]
32.Prepreg fibers70% strength when compared with new fibers[343]
33.Filler material for fiberglass/epoxy compositesMetallized food packaging plastic waste0.75 wt.% of char particles improved the modulus of elasticity of panels by approximately 22%, compared with a pure sample.[344]
34.Hybrid fillers for cement industryTextile wasteChar particles (0.05 wt.%) was used as a single filler and hybrid fillers (CNTs/CB and graphene/CB: 50/50) to enhance the properties of cement paste[345]
S. NoProductsPrecursor materialRemarks (if any)Ref.
1.Battery electrodeBiomass (various)Review article[312]
2.Rice huskLithium ion batteries[313]
3.BambooLithium ion batteries[314]
4.shaddock peelSodium ion batteries[315]
5.Coffee groundsSodium ion batteries[316]
6.Supercapacitor electrodeRice huskRHC: KOH = 1:5 by mass was used for activation[317]
7.CarrotZnCl2 as activation agent[318]
8.Biomass (various)Review article[319]
9.Coconut shell[320]
10.Tobacco[321]
11.Tamarind fruit shellActivation of char was done by treating the precursor with KOH[322]
12.Dye sensitized solar panel (counter electrode)Filter paper facial tissue[323]
13.Fish wastePt-free counter electrode[324]
14.Coconut shellAnthocyanin dye extracted from pomegranate juice[325]
15.Anchovy[326]
16.Water filtration or adsorbentsBiomass (various)Review article[327]
17.Nutshells (Almond, English Walnut, Pecan)[328]
18.Apple pulpAdsorption of lead and zinc[329]
19.Fertilizer wasteHeavy metal removal from fixed bed reactor[330]
20.Chickpea[331]
21.Municipal organic solid waste[332]
22.Coconut button[333]
23.Municipal sewage sludge[334]
24.Human hairSensor for dopamine and ascor-bic acid[335]
25.Polyethylene terephthalate (PET) bottlesDetection of carbofuran phenol[336]
26.AmlaSensor for ascorbic acid, dopamine, uric acid and nitrite[337]
27.Onion peelSensor for progesterone[338]
28.Biomass (various)Review article[339]
29.Tetra pak wasteMercury adsorption from water[340]
30.CF manufacturingCotton[341]
31.Prepreg fibersPrepreg is ‘pre-impregnated’ composite fibers[342]
32.Prepreg fibers70% strength when compared with new fibers[343]
33.Filler material for fiberglass/epoxy compositesMetallized food packaging plastic waste0.75 wt.% of char particles improved the modulus of elasticity of panels by approximately 22%, compared with a pure sample.[344]
34.Hybrid fillers for cement industryTextile wasteChar particles (0.05 wt.%) was used as a single filler and hybrid fillers (CNTs/CB and graphene/CB: 50/50) to enhance the properties of cement paste[345]

Catalytic pyrolysis

Various catalysts are used during waste pyrolysis that can potentially increase the oil, gas or char fractions, as desirable in the process. Catalytic pyrolysis of plastic waste is typically carried out in presence of natural/modified zeolites to produce pyrolysis oils, which can be used as transportation fuel by mixing or blending with conventional fuels [346, 347]. Other catalysis that are being extensively studied include metal oxides and bimetallics [152]. More information about catalytic pyrolysis of MSW and plastic wastes can be found in these recent articles [347–349].

Semi-cokes/mesophase carbon from pyrolysis of pitch

It is not possible to commercially exploit all of the crude petroleum of the barrel for commercial purposes and the various distillation and cracking processes produce a huge amount of residues within the refinery, the disposal of the same is of major concern [350]. These residues are rich in aromatics and has high C/H ratio, hence can be a good feedstock for mesophase carbon. When these residues are heat treat at around 450°C, they convert into a pitch-like isotropic material having a consistency similar to liquid crystals. With increasing temperature, small spheres appear in the pitch-like mass, which grow with time. At some stage in the heating process, the spheres will replace a large part of the pitch-like material and interfere with one another’s enlargement and a ‘mosaic’ begins to form by coalescence when all of the isotropic pitch-like material is replaced by the anisotropic material or mesophase and the mosaic is complete, the mesophase solidifies into ‘semi-coke’, which is readily graphitizable [351]. With further heat treatment (1400°C), this carbonaceous mesophase coalesces to a state of bulk mesophase before solidification to ‘green coke’ with further loss of volatile compounds [350]. However, apart from this regular trend, many different behaviors have been observed for varying compositions of the feedstock. The petroleum residues are a mixture of more than 1000 molecular compounds (numbers differ in literature) and contain mixtures of aliphatic and aromatic compounds. To obtain high-quality cokes acceptable for industrial usage (as electrodes for steel industry), high aromaticity in the precursor is essential. Before getting converted to green coke at higher temperatures, this pitch material, known as mesophase pitch can be a good precursor for preparation of high-performance carbon materials [352] like pitch-derived coke [353], mesocarbon microbeads (MCMB), CF [3, 23, 194], carbon foams and carbon composites [354]. A summary of various carbon forms obtained from mesophase pitches and their respective applications is listed in Table 9.

Table 9:

Different types of carbon materials obtained by pyrolysis of mesophase pitch and their applications

S. No.Carbon formPrecursor sourcePyrolysis parametersRemarks (if any)Ref.
1.MCMBCo-pyrolysis of coal tar pitch and direct coal liquefaction residue sTemperature; 440°C, 8 h, N2 gas.Li-ion battery, anode material[3]
2.Naphthalene isotropic pitchSuspension method, HF/BF3 catalyst, temperature; 1000°CLi-ion battery, anode[355]
3.Petroleum pitchCarbonization temperature; 400°C, 4 h, N2 Gas, heat treatment in vacuum, 380°C, 30 minLi-ion battery, anode material[356]
4.Coal tar pitchCarbonization temperature; 700°C, 2 h, N2 gasSodium-ion battery, anode material[357]
5.Catalytic cracking oil residue
  • Temperature; 350°C (30 min)

  • 400°C (40 min)

  • 400°C (4–9 h)

Investigation of the relationship between olefins and the coalescence of mesophase spheres[358]
6.Carbon foamsCoal pitchCarbonization temperature; 450°C, N2 gasInvestigation of acoustic properties[359]
7.Coal tar pitchCarbonization temperature; 600°C, 2 h.Thermal insulation[360]
8.Coal tar pitch modified with HNO3 and H2SO4carbonization temperature; 2000°C, N2 gasMicrostructure investigations[361]
9.Hierarchical porous carbonsCoal tar pitch,
  • Final temperature, 800°C, 2 h,

  • Ramp rate, 2°C/min

  • anhydrous aluminium chloride (catalyst)

Supercapacitor electrode[4]
10.MCMB/carbon foamsCoal tar pitch
  • Final temperature; 440°C,

  • N2 gas, 12 h, foaming pressure, 3 MPa

Investigation of microstructure and properties[362]
11.Activated carbonsPetroleum residues (decanted oil and ethylene tars)Temperature; 400–460°C, 2 h,4 h, and 6 h, respectivelyMethane adsorption[363]
12.Mesoporous soft carbonsNapthalene-based synthetic pitchtemperature; 350–800°C, 5°C/min, 2 h, N2 gasAnode material, sodium-ion batteries[364]
13.Needle cokeCoal tar pitchTemperature; room temperature to 1400°C, 5°C/min, 1 h holding time, N2 gasGreen coke with aromatic index of 0.95–0.98 obtained.[365]
14.GraphenePetroleum mesophase pitchActivated carbon: temperature; room temperature to 800°C, holding time; 2 h,Graphene was prepared from mesophase pitch derived activated carbon by exfoliation (treated with N-methyl-2-pyrrolidone [NMP])[366]
15.N doped mesoporous carbonMesophase pitch and polypyrolle (N source)Final temperatures; 600°C, 700°C, 800°C, 10°C/min, N2 gasSupercapacitor electrode[367]
S. No.Carbon formPrecursor sourcePyrolysis parametersRemarks (if any)Ref.
1.MCMBCo-pyrolysis of coal tar pitch and direct coal liquefaction residue sTemperature; 440°C, 8 h, N2 gas.Li-ion battery, anode material[3]
2.Naphthalene isotropic pitchSuspension method, HF/BF3 catalyst, temperature; 1000°CLi-ion battery, anode[355]
3.Petroleum pitchCarbonization temperature; 400°C, 4 h, N2 Gas, heat treatment in vacuum, 380°C, 30 minLi-ion battery, anode material[356]
4.Coal tar pitchCarbonization temperature; 700°C, 2 h, N2 gasSodium-ion battery, anode material[357]
5.Catalytic cracking oil residue
  • Temperature; 350°C (30 min)

  • 400°C (40 min)

  • 400°C (4–9 h)

Investigation of the relationship between olefins and the coalescence of mesophase spheres[358]
6.Carbon foamsCoal pitchCarbonization temperature; 450°C, N2 gasInvestigation of acoustic properties[359]
7.Coal tar pitchCarbonization temperature; 600°C, 2 h.Thermal insulation[360]
8.Coal tar pitch modified with HNO3 and H2SO4carbonization temperature; 2000°C, N2 gasMicrostructure investigations[361]
9.Hierarchical porous carbonsCoal tar pitch,
  • Final temperature, 800°C, 2 h,

  • Ramp rate, 2°C/min

  • anhydrous aluminium chloride (catalyst)

Supercapacitor electrode[4]
10.MCMB/carbon foamsCoal tar pitch
  • Final temperature; 440°C,

  • N2 gas, 12 h, foaming pressure, 3 MPa

Investigation of microstructure and properties[362]
11.Activated carbonsPetroleum residues (decanted oil and ethylene tars)Temperature; 400–460°C, 2 h,4 h, and 6 h, respectivelyMethane adsorption[363]
12.Mesoporous soft carbonsNapthalene-based synthetic pitchtemperature; 350–800°C, 5°C/min, 2 h, N2 gasAnode material, sodium-ion batteries[364]
13.Needle cokeCoal tar pitchTemperature; room temperature to 1400°C, 5°C/min, 1 h holding time, N2 gasGreen coke with aromatic index of 0.95–0.98 obtained.[365]
14.GraphenePetroleum mesophase pitchActivated carbon: temperature; room temperature to 800°C, holding time; 2 h,Graphene was prepared from mesophase pitch derived activated carbon by exfoliation (treated with N-methyl-2-pyrrolidone [NMP])[366]
15.N doped mesoporous carbonMesophase pitch and polypyrolle (N source)Final temperatures; 600°C, 700°C, 800°C, 10°C/min, N2 gasSupercapacitor electrode[367]
Table 9:

Different types of carbon materials obtained by pyrolysis of mesophase pitch and their applications

S. No.Carbon formPrecursor sourcePyrolysis parametersRemarks (if any)Ref.
1.MCMBCo-pyrolysis of coal tar pitch and direct coal liquefaction residue sTemperature; 440°C, 8 h, N2 gas.Li-ion battery, anode material[3]
2.Naphthalene isotropic pitchSuspension method, HF/BF3 catalyst, temperature; 1000°CLi-ion battery, anode[355]
3.Petroleum pitchCarbonization temperature; 400°C, 4 h, N2 Gas, heat treatment in vacuum, 380°C, 30 minLi-ion battery, anode material[356]
4.Coal tar pitchCarbonization temperature; 700°C, 2 h, N2 gasSodium-ion battery, anode material[357]
5.Catalytic cracking oil residue
  • Temperature; 350°C (30 min)

  • 400°C (40 min)

  • 400°C (4–9 h)

Investigation of the relationship between olefins and the coalescence of mesophase spheres[358]
6.Carbon foamsCoal pitchCarbonization temperature; 450°C, N2 gasInvestigation of acoustic properties[359]
7.Coal tar pitchCarbonization temperature; 600°C, 2 h.Thermal insulation[360]
8.Coal tar pitch modified with HNO3 and H2SO4carbonization temperature; 2000°C, N2 gasMicrostructure investigations[361]
9.Hierarchical porous carbonsCoal tar pitch,
  • Final temperature, 800°C, 2 h,

  • Ramp rate, 2°C/min

  • anhydrous aluminium chloride (catalyst)

Supercapacitor electrode[4]
10.MCMB/carbon foamsCoal tar pitch
  • Final temperature; 440°C,

  • N2 gas, 12 h, foaming pressure, 3 MPa

Investigation of microstructure and properties[362]
11.Activated carbonsPetroleum residues (decanted oil and ethylene tars)Temperature; 400–460°C, 2 h,4 h, and 6 h, respectivelyMethane adsorption[363]
12.Mesoporous soft carbonsNapthalene-based synthetic pitchtemperature; 350–800°C, 5°C/min, 2 h, N2 gasAnode material, sodium-ion batteries[364]
13.Needle cokeCoal tar pitchTemperature; room temperature to 1400°C, 5°C/min, 1 h holding time, N2 gasGreen coke with aromatic index of 0.95–0.98 obtained.[365]
14.GraphenePetroleum mesophase pitchActivated carbon: temperature; room temperature to 800°C, holding time; 2 h,Graphene was prepared from mesophase pitch derived activated carbon by exfoliation (treated with N-methyl-2-pyrrolidone [NMP])[366]
15.N doped mesoporous carbonMesophase pitch and polypyrolle (N source)Final temperatures; 600°C, 700°C, 800°C, 10°C/min, N2 gasSupercapacitor electrode[367]
S. No.Carbon formPrecursor sourcePyrolysis parametersRemarks (if any)Ref.
1.MCMBCo-pyrolysis of coal tar pitch and direct coal liquefaction residue sTemperature; 440°C, 8 h, N2 gas.Li-ion battery, anode material[3]
2.Naphthalene isotropic pitchSuspension method, HF/BF3 catalyst, temperature; 1000°CLi-ion battery, anode[355]
3.Petroleum pitchCarbonization temperature; 400°C, 4 h, N2 Gas, heat treatment in vacuum, 380°C, 30 minLi-ion battery, anode material[356]
4.Coal tar pitchCarbonization temperature; 700°C, 2 h, N2 gasSodium-ion battery, anode material[357]
5.Catalytic cracking oil residue
  • Temperature; 350°C (30 min)

  • 400°C (40 min)

  • 400°C (4–9 h)

Investigation of the relationship between olefins and the coalescence of mesophase spheres[358]
6.Carbon foamsCoal pitchCarbonization temperature; 450°C, N2 gasInvestigation of acoustic properties[359]
7.Coal tar pitchCarbonization temperature; 600°C, 2 h.Thermal insulation[360]
8.Coal tar pitch modified with HNO3 and H2SO4carbonization temperature; 2000°C, N2 gasMicrostructure investigations[361]
9.Hierarchical porous carbonsCoal tar pitch,
  • Final temperature, 800°C, 2 h,

  • Ramp rate, 2°C/min

  • anhydrous aluminium chloride (catalyst)

Supercapacitor electrode[4]
10.MCMB/carbon foamsCoal tar pitch
  • Final temperature; 440°C,

  • N2 gas, 12 h, foaming pressure, 3 MPa

Investigation of microstructure and properties[362]
11.Activated carbonsPetroleum residues (decanted oil and ethylene tars)Temperature; 400–460°C, 2 h,4 h, and 6 h, respectivelyMethane adsorption[363]
12.Mesoporous soft carbonsNapthalene-based synthetic pitchtemperature; 350–800°C, 5°C/min, 2 h, N2 gasAnode material, sodium-ion batteries[364]
13.Needle cokeCoal tar pitchTemperature; room temperature to 1400°C, 5°C/min, 1 h holding time, N2 gasGreen coke with aromatic index of 0.95–0.98 obtained.[365]
14.GraphenePetroleum mesophase pitchActivated carbon: temperature; room temperature to 800°C, holding time; 2 h,Graphene was prepared from mesophase pitch derived activated carbon by exfoliation (treated with N-methyl-2-pyrrolidone [NMP])[366]
15.N doped mesoporous carbonMesophase pitch and polypyrolle (N source)Final temperatures; 600°C, 700°C, 800°C, 10°C/min, N2 gasSupercapacitor electrode[367]

Special cases

Although the term pyrolysis is predominantly used in the context of organic materials, there are certain examples where pyrolysis is performed on inorganic solids/liquids as well. Synthesis of 2D nanomaterials like graphitic carbon nitride from pyrolysis of urea [368], molybdenum sulfide by CVD [369] and thin films by CVD of inorganic precursors [370] are a few examples. Another variation of pyrolysis known as spray pyrolysis [371–373], in which precursors in liquid phase are sprayed through an atomizer onto a heated substrate (250–500°C) [374], mainly aimed at deposition of thin and thick semiconductor films for solar cells applications [375–377]. However, at present, this process has been extended to deposition of thin films for sensors [378], solid oxide fuel cells [379] applications as well. Spray pyrolysis technique has also been utilized in the synthesis of various nanomaterials apart from thin films [380–382] which is beyond the scope of this paper due to vastness of the topic. Another term known as ‘hydropyrolysis’, that is, pyrolysis in presence of hydrogen at high pressure, is predominantly performed on biomass to obtain biofuels/chemicals for industrial use in presence of a catalyst. Hydrogen is used as a reducing agent to form hydrogenated radicals by reacting with the volatiles and to remove oxygen in the form of water, CO and CO2, resulting in hydrocarbon generation [383]. However, hydropyrolysis in itself is a vast topic and is beyond the scope of this paper.

CONCLUSION AND WAY FORWARD

Pyrolysis is extensively used in different applications that are covered in this review in terms of their fundamental principles, history, industrial relevance and process parameters. Evidently, these applications not only belong to entirely different scientific communities, their target products and production scales also widely vary. One important conclusion is that pretty much all synthetic carbon materials, bulk or nano-scale, are derived from organic precursors via the pyrolysis process. Given the significance of advanced carbon allotropes in the cutting-edge technology, there is a compelling need for (i) reducing the cost of pyrolysis, (ii) improving the efficiency of the process and (iii) development of integrated pyrolysis systems. Lowering the energy consumption during pyrolysis is not straightforward, but is possible with the use of sophisticated nano-scale catalysts that can potentially lead to an overall cost reduction. One challenge is to get rid of the catalyst particles through post-processing with a high yield, which demands more focused research. Generally, catalysts can also facilitate an increase in the overall process efficiency. While the idea of efficiency may differ based on the application area, tuning of the underlying process parameters can always be of help. For this purpose, a comprehensive understanding of the pyrolysis mechanism for a given precursor is essential. Key concepts pertaining to this are covered in detail in this review.

The development of the integrated pyrolysis systems may serve multiple purposes. Plenty of work has lately commenced in this direction, where the goal is to further pyrolyze the byproduct(s) of one pyrolytic process. A good example is carbon nanomaterial production via secondary pyrolysis of the synthetic gas obtained during waste pyrolysis. Such innovative ideas need technological support from both academia and industry, for example, an optimized reactor design suitable for the quantity of the feed. Based on the information available in the literature, such multi-stage pyrolysis equipments are already proving to be extremely helpful in improving the commercial viability of the waste treatment plants. Some other integrated processes such as the microbial bioprocessing of pyrolytic oils have also lately gained attention for the generation of fuel with a higher calorific value. An additional future prospect is the quality enhancement of low-grade biochars by increasing the pyrolysis temperature and ensuring a strictly inert environment during the process. The know-how is already available with the activated carbon industry and researchers are rapidly coming up with very promising results. For large-scale pyrolysis, plasma-assisted processes and/or solar energy supported plants are also recommended. The age-old process of pyrolysis is expected to play a major role in the near future in the carbon materials science as well as the expansion of the sustainable energy solutions.

Acknowledgments

M.D. would like to thank the Ministry of Education, Government of India, for her doctoral fellowship. S.S. acknowledges the financial support from the Seed Research Grant No. IITM/SG/SWS/69, Indian Institute of Technology, Mandi.

AUTHORS’ CONTRIBUTIONS

M.D. prepared the initial draft including figures and tables as well as contributed to editing and finalizing the manuscript. S.R. contributed in drafting the waste pyrolysis section. S.S. conceptualized, edited and finalized the manuscript.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

REFERENCES

1

Manawi
Y
,
Ihsanullah
,
Samara
A
et al.
A review of carbon nanomaterials’ synthesis via the chemical vapor deposition (CVD) method
.
Materials
2018
;
11
:
822
.

2

Gracio
JJ
,
Fan
QH
,
Madaleno
JC.
Diamond growth by chemical vapour deposition
.
J Phys D Appl Phys
2010
;
43
:
374017
.

3

Yan
B
,
Wang
G.
Mechanisms and characteristics of mesocarbon microbeads prepared by co-carbonization of coal tar pitch and direct coal liquefaction residue
.
Int J Coal Sci Technol
2019
;
6
:
633
42
.

4

Wang
H
,
Zhu
H
,
Wang
S
et al.
Dicarbonyl-tuned microstructures of hierarchical porous carbons derived from coal-tar pitch for supercapacitor electrodes
.
R Soc Chem
2019
;
9
:
20019
28
.

5

Moore
AW.
Pyrolytic carbon and graphite. In:
Jürgen Buschow
KH
,
Cahn
RW
,
Flemings
MC
et al. (eds.),
Encyclopedia of Materials: Science and Technology
.
Oxford
:
Elsevier
,
2001
,
7933
77
.

6

Pierson
HO.
Handbook of Carbon, Graphite, Diamonds and Fullerenes: Processing, Properties and Applications. Materials Science and Process Technology Series Electronic
.
Elsevier Science
,
2012
.

7

Sharma
S.
Glassy carbon: A promising materials for micro- and nanomanufacturing
.
Materials
2018
;
11
:
1857
.

8

Nimbalkar
S
,
Fuhrer
E
,
Silva
P
et al.
Glassy carbon microelectrodes minimize induced voltages, mechanical vibrations, and artifacts in magnetic resonance imaging
.
Microsyst Nanoeng
2019
;
5
:
61
.

9

Zakhurdaeva
A
,
Dietrich
P-I
,
Holscher
H
et al.
Custom-designed glassy carbon tips for atomic force microscopy
.
Micromachines
2017
;
8
:
285
.

10

Mamleyev
ER
,
Heissler
S
,
Nefedov
A
et al.
Laser-induced hierarchical carbon patterns on polyimide substrates for flexible urea sensors
.
NPJ Flexible Electronics
2019
;
3
:
2
.

11

Goshi
N
,
Castagnola
E
,
Vomero
M
et al.
Glassy carbon MEMS for novel origami-styled 3d integrated intracortical and epicortical neural probes
.
J Micromech Microeng
,
2018
;
28
:
065009
.

12

Czajczynska
D
,
Anguilano
L
,
Ghazal
H
et al.
Potential of pyrolysis processes in the waste management sector
.
Therm Sci Eng Prog
2017
;
3
:
171
97
.

13

Ahmad
I
,
Khan
MI
,
Khan
H
et al.
Pyrolysis study of polypropylene and polyethylene into premium oil products
.
Int J Green Energy
2015
;
12
:
663
71
.

14

Larter
SR
,
Horsfield
B.
Determination of Structural Components of Kerogens by the Use of Analytical Pyrolysis Methods
.
Boston (MA)
:
Springer US
,
1993
,
271
87
.

15

Herring
AM
,
[Thomas McKinnon
J
,
Gneshin
KW
et al.
Detection of reactive intermediates from and characterization of biomass char by laser pyrolysis molecular beam mass spectroscopy. (Fundamental mechanisms of biomass, pyrolysis and oxidation.)
Fuel
2004
;
83
:
1483
94
.

16

Leinweber
P
,
Schulten
H-R
Advances in analytical pyrolysis of soil organic matter
.
J Anal Appl Pyrol
1999
;
49
:
359
83
.

17

Bhuyan
MSA
,
Uddin
MN
,
Islam
MM
et al.
Synthesis of graphene
.
Int Nano Lett
2016
;
6
:
65
83
.

18

Mattevi
C
,
Kim
H
,
Chhowalla
M.
A review of chemical vapour deposition of graphene on copper
.
J Mater Chem
,
201
;
21
:
3324
34
.

19

Endo
M
,
Muramatsu
H
,
Hayashi
T
et al.
‘Buckypaper’ from coaxial nanotubes
.
Nature
2005
;
433
:
476
.

20

Ahmad
M
,
Silva
SRP.
Low temperature growth of carbon nanotubes—a review
.
Carbon
2020
;
158
:
24
44
.

21

Tibbetts
GG.
Vapor-grown carbon fibers: status and prospects. (Carbon fibers and composites.)
Carbon
1989
;
27
:
745
7
.

22

Peebles
LH.
Carbon Fibers: Formation, Structure, and Properties
.
CRC Press
,
2018
.

23

Inagaki
M.
New Carbons—Control of Structure and Functions
.
Elsevier Science
,
2000
.

24

Janus
M.
Chapter 3—DLC layers created using CVD techniques and their application. In:
Mandracci
P
(ed.),
Chemical Vapor Deposition for Nanotechnology
.
Rijeka
:
IntechOpen
,
2019
.

25

Walker
PL
,
Thrower
PA.
Chemistry & Physics of Carbon
.
Taylor & Francis
,
1975
.

26

Chambers
CR
,
Huges
TV
. Manufacture of carbon filaments. 6 May 1889. US Patent 4,054,480A.

27

Bacon
R.
Growth, structure, and properties of graphite whiskers
.
J Appl Phys
1960
;
31
:
283
90
.

28

Pierson
HO.
Handbook of Chemical Vapor Deposition
. 2nd edn—Principles, Technology and Applications. Materials Science and Process Technology.
Elsevier Science
,
1999
.

29

Somiya
S.
Hydrothermal Reactions for Materials Science and Engineering: An Overview of Research in Japan
.
Netherlands
:
Springer
,
2012
.

30

Sharma
S
,
Sharma
A
,
Cho
Y-K
et al.
Increased graphitization in electrospun single suspended carbon nanowires integrated with carbon-mems and carbon-nems platforms
.
ACS Appl Mater Interfaces
2012
;
4
:
34
9
.

31

Yan
Z
,
Joshi
R
,
You
Y
et al.
Seeded growth of ultrathin carbon films directly onto silicon substrates
.
ACS Omega
2021
;
6
:
8829
36
.

32

Schaefer
W
,
Fitzer
E
,
Meuller
K.
The Chemistry of the Pyrolytic Conversion of Organic Compounds to Carbon: Chemistry and Physics of Carbon
. Vol.
7
.
New York
:
Marcel Dekker, Inc
.,
1971
.

33

Kucora
I
,
Paunjoric
P
,
Tolmac
J
et al.
Coke formation in pyrolysis furnaces in the petrochemical industry
.
Petrol Sci Technol
2017
;
35
:
213
21
.

34

Egwuonwu
CC
,
Arinze
RU
,
Agbata
PC
et al.
Waste tire pyrolysis product: An alternative to petrochemical feedstock
.
Asian J Phys Chem Sci
,
2021
;
40
50
.

35

Olsvik
O
,
Rokstad
OA
,
Holmen
A.
Pyrolysis of methane in the presence of hydrogen
.
Chem Eng Technol
1995
;
18
:
349
58
.

36

Kan
T
,
Strezov
V
,
Evans
TJ.
Lignocellulosic biomass pyrolysis: A review of product properties and effects of pyrolysis parameters
.
Renew Sustain Energy Rev
2016
;
57
:
1126
40
.

37

Yusof
N
,
Ismail
AF.
Post spinning and pyrolysis processes of polyacrylonitrile (pan)-based carbon fiber and activated carbon fiber: A review
.
J Anal Appl Pyrol
2012
;
93
:
1
13
.

38

Martınez
JD
,
Puy
N
,
Murillo
R
et al.
Waste tyre pyrolysis—a review
.
Renew Sustain Energy Rev
2013
;
23
:
179
213
.

39

Fonts
I
,
Gea
G
,
Azuara
M
et al.
Sewage sludge pyrolysis for liquid production: A review
.
Renew Sustain Energy Rev
2012
;
16
:
2781
805
.

40

Wang
G
,
Dai
Y
,
Yang
H
et al.
A review of recent advances in biomass pyrolysis
.
Energy Fuels
2020
;
34
:
15557
78
.

41

Dai
L
,
Wang
Y
,
Liu
Y
et al.
A review on selective production of value-added chemicals via catalytic pyrolysis of lignocellulosic biomass
.
Science Total Environ
2020
;
749
:
142386
.

42

Harris
PJF.
Transmission electron microscopy of carbon: A brief history. J
Caron Res
2018
;
4
:
4
.

43

Walker
PL
Jr
Presland
AEB.
Growth of single crystal graphite by pyrolysis of acetylene over metals
.
Carbon
1969
;
7
:
1
8
.

44

Clark
CH.
Primary batteries
.
Electric Eng
1950
;
69
:
515
8
.

45

Hazen
RM
,
Jones
AP
,
Baross
JA.
Carbon in Earth
.
Boston
:
De Gruyter, Inc
.,
2018
.

46

Bonijoly
M
,
Oberlin
M
,
Oberlin
A.
A possible mechanism for natural graphite formation
.
Int J Coal Geol
1982
;
1
:
283
12
.

47

Ohtomo
Y
,
Kakegawa
T
,
Ishida
A
et al.
Evidence for biogenic graphite in early Archaean ISUA metasedimentary rocks
.
Nat Geosci
2014
;
7
:
25
8
.

48

Baker
RR.
A review of pyrolysis studies to unravel reaction steps in burning tobacco
.
J Anal Appl Pyrol
1987
;
11
:
555
73
.

49

Learmonth
GS
,
Nesbitt
A
,
Thwaite
DG.
Flammability of plastics I. Relation between pyrolysis and burning
.
Br Polym J
1969
;
1
:
149
53
.

50

Cundy
VA.
Combustion, 2nd edition by Irvin Glassman, Academic Press, Inc., Orlando, FL (1987)
.
Environ Prog
1993
;
12
:
M6
7
.

51

Jenkins
GM
,
Jenkins
A
,
Kawamura
K.
Polymeric Carbons: Carbon Fibre, Glass and Char
.
Cambridge University Press
,
1976
.

52

Amin
MN
,
Li
Y
,
Lu
X.
In situ catalytic pyrolysis of low-rank coal for the conversion of heavy oils into light oils
.
Adv Mater Sci Eng
2017
;
5612852
.

53

Chen
J
,
Niksa
S.
The effects of secondary reactions on nitrogen distributions from rapid coal pyrolysis. In:
International Energy Agency Coal Research Ltd. (ed.), 1991 International Conference on Coal Science Proceedings
.
Butterworth-Heinemann
,
1991
,
580
3
.

54

Richter
H
,
Mamic
J
,
Morsy
M
et al. Chapter 11—Coke production from low rank coals. In: Luo Z and Agraniotis M (eds), Low-Rank Coals for Power Generation, Fuel and Chemical Production. Woodhead Publishing,
2017
,
269
99
.

55

Bianco
A
,
Cheng
H-M
,
Enoki
T
et al.
All in the graphene family—a recommended nomenclature for two-dimensional carbon materials
.
Carbon
2013
;
65
:
1
6
.

56

Collard
F-X
,
Blin
J.
A review on pyrolysis of biomass constituents: Mechanisms and composition of the products obtained from the conversion of cellulose, hemicelluloses and lignin
.
Renew Sustain Energy Rev
2014
;
38
:
594
608
.

57

Bridgwater
AV.
Review of fast pyrolysis of biomass and product upgrading. (Overcoming barriers to bioenergy: outcomes of the bioenergy network of excellence 2003–2009.)
Biomass Bioenergy
2012
;
38
:
68
94
.

58

He
M
,
Xiao
B
,
Liu
S
et al.
Syngas production from pyrolysis of municipal solid waste (MSW) with dolomite as downstream catalysts
.
J Anal Appl Pyrol
2010
;
87
:
181
7
.

59

Lu
J-S
,
Chang
Y
,
Poon
C-S
et al.
Slow pyrolysis of municipal solid waste (MSW): A review
.
Bioresour Technol
2020
;
312
:
123615
.

60

Korai
Y
,
Mochida
I.
Preparation and properties of carbonaceous mesophase—soluble mesophase produced from A240 and coal tar pitch
.
Carbon
1985
;
23
:
97
103
.

61

Liu
D
,
Lou
B
,
Li
M
et al.
Study on the preparation of mesophase pitch from modified naphthenic vacuum residue by direct thermal treatment
.
Energy Fuels
2016
;
30
:
4609
18
.

62

Branca
C
,
Blasi
CD.
Multistep mechanism for the devolatilization of biomass fast pyrolysis oils
.
Ind Eng Chem Res
2006
;
45
:
5891
9
.

63

Vomero
M
,
Mondragon
NC
,
Stieglitz
T
. Electrochemical characterization and surface analysis of activated glassy carbon neural electrodes. In: 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC),
2019
,
3923
6
.

64

Rial-Otero
R
,
Galesio
M
,
Capelo
J-L
et al.
A review of synthetic polymer characterization by pyrolysis–GC–MS
.
Chromatographia
2009
;
70
:
339
48
.

65

Sharma
S
,
Shyam Kumar
CN
,
Korvink
JG
et al.
Evolution of glassy carbon microstructure: In situ transmission electron microscopy of the pyrolysis process
.
Sci Rep
2018
;
8
:
16282
.

66

Allard
LF
,
Overbury
SH
,
Bigelow
WC
et al.
Novel MEMS-based gas-cell/heating specimen holder provides advanced imaging capabilities for in situ reaction studies
.
Microsc Microanal
2012
;
18
:
656
66
.

67

Meuzelaar
HLC
,
Haverkamp
J
,
Hileman
FD.
Pyrolysis Mass Spectrometry of Recent and Fossil Biomaterials: Compendium and Atlas.
Vol. 3—Techniques and Instrumentation in Analytical Chemistry
.
Amsterdam
:
Elsevier Scientific Pub. Co
,
1982
.

68

Hugo
H
,
Garza
P
,
Pivak
Y
et al.
MEMS-based sample carriers for simultaneous heating and biasing experiments: A platform for in-situ TEM analysis
. In:
2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS)
,
2017
,
2155
8
.

69

Kumar
M
,
Srivastava
N
,
Upadhyay
SN
et al.
Thermal degradation of dry kitchen waste: kinetics and pyrolysis products
.
Biomass Convers Biorefinery
2021
:
1
18
.

70

Zhang
Y
,
Ji
G
,
Chen
C
et al.
Liquid oils produced from pyrolysis of plastic wastes with heat carrier in rotary kiln
.
Fuel Process Technol
2020
;
206
:
106455
.

71

Khan
MZH
,
Sultana
M
,
Al-Mamun
MR
et al.
Pyrolytic waste plastic oil and its diesel blend: Fuel characterization
.
J Environ Public Health
2016
;
2016
:
1
6
.

72

Sowmya Dhanalakshmi
C
,
Madhu
P.
Biofuel production of neem wood bark (Azadirachta indica) through flash pyrolysis in a fluidized bed reactor and its chromatographic characterization
.
Energy Sources A: Recovery Util Environ Eff
2021
;
43
:
428
43
.

73

Gholizadeh
M
,
Li
C
,
Zhang
S
et al.
Progress of the development of reactors for pyrolysis of municipal waste
.
Sustain Energy Fuels
2020
;
4
:
5885
915
.

74

Cai
X
,
Cai
H
,
Shang
C
et al.
Two-stage pyrolysis/gasification and plasma conversion technology for the utilization of solid waste
.
IEEE Trans Plasma Sci
2021
;
49
:
191
213
.

75

Gueret
C
,
Daroux
M
,
Billaud
F.
Methane pyrolysis: thermodynamics
.
Chem Eng Sci
1997
;
52
:
815
27
.

76

Cullis
CF
,
Franklin
NH
,
Gaydon
AG.
The pyrolysis of acetylene at temperatures from 500 to 1000°C
.
Proc R Soc Lond Ser A Math Phys Sci
1964
;
280
:
139
52
.

77

Aronowitz
D
,
Naegeli
DW
,
Glassman
I.
Kinetics of the pyrolysis of methanol
.
J Phys Chem
1977
;
81
:
2555
9
.

78

Lersmacher
B
,
Lydtin
H
,
Knippenberg
WF
et al.
Thermodynamische betrachtungen zur kohlenstoffabscheidung bei der pyrolyse gasf¨ormiger kohlenstoffverbindungen
.
Carbon
1967
;
5
:
205
17
.

79

Sharma
P
,
Pavelyev
V
,
Kumar
S
et al.
Analysis on the synthesis of vertically aligned carbon nanotubes: growth mechanism and techniques
.
J Mater Sci Mater Electron
2020
;
31
:
4399
443
.

80

Thrower
PA.
Chemistry & Physics of Carbon. Taylor & Francis,
1984
.

81

Lewis
IC.
Chemistry of carbonization
.
Carbon
1982
;
20
:
519
29
.

82

Poutsma
ML.
Free-radical thermolysis and hydrogenolysis of model hydrocarbons relevant to processing of coal
.
Energy Fuels
1990
;
4
:
113
31
.

83

Poutsma
ML.
Fundamental reactions of free radicals relevant to pyrolysis reactions
.
J Anal Appl Pyrol
2000
;
54
:
5
35
.

84

Jenkins
RG
,
Nandi
SP
,
Walker
PL.
Reactivity of heat-treated coals in air at 500°C
.
Fuel
1973
;
52
:
288
93
.

85

Biryukova
GP
,
Shablygin
MV
,
Mikhailov
NV
et al.
Relationship between the conditions of pyrolysis and the structural and chemical transformation of cellulose hydrate
.
Polym Sci USSR
1973
;
15
:
1762
6
.

86

Ōtani
S
,
Yamada
K
,
Koitabashi
T
et al.
On the raw materials of MP carbon fiber
.
Carbon
1966
;
4
:
425
32
.

87

Khorasheh
F
,
Gray
MR.
High-pressure thermal cracking of n-hexadecane
.
Ind Eng Chem Res
1993
;
32
:
1853
63
.

88

Shyam Kumar
CN
,
Kiran Chakravadhanula
VS
,
Riaz
A
et al.
Understanding the graphitization and growth of free-standing nanocrystalline graphene using in situ transmission electron microscopy
.
Nanoscale
2017
;
9
:
12835
42
.

89

Zhu
G
,
Zhu
X
,
Xiao
Z
et al.
Study of cellulose pyrolysis using an in situ visualization technique and thermogravimetric analyzer
.
J Anal Appl Pyrol
2012
;
94
:
126
30
.

90

Li
M
,
Zeng
F
,
Chang
H
et al.
Aggregate structure evolution of low-rank coals during pyrolysis by in-situ X-ray diffraction
.
Int J Coal Geol
2013
;
116–117
:
262
9
.

91

Jurkiewicz
K
,
Duber
S
,
Fischer
HE
et al.
Modelling of glass-like carbon structure and its experimental verification by neutron and X-ray diffraction
.
J Appl Crystallogr
2017
;
50
:
36
48
.

92

Lin
J-F
,
Santoro
M
,
Struzhkin
VV
et al.
In situ high pressure–temperature Raman spectroscopy technique with laser-heated diamond anvil cells
.
Rev Sci Instruments
2004
;
75
:
3302
6
.

93

Anca-Couce
A
,
Tsekos
C
,
Retschitzegger
S
et al.
Biomass pyrolysis tga assessment with an international round robin
.
Fuel
2020
;
276
:
118002
.

94

Kolawole
FO
,
Kolawole
SK
,
Varela
LB
et al. Diamond-like carbon (DLC) coatings for automobile applications. Engineering Applications of Diamond [Working Title]. IntechOpen,
2020
.

95

Shimanoe
H
,
Mashio
T
,
Nakabayashi
K
et al.
Manufacturing spinnable mesophase pitch using direct coal extracted fraction and its derived mesophase pitch based carbon fiber
.
Carbon
2020
;
158
:
922
9
.

96

Sevilla
M
,
Dıez
N
,
Fuertes
AB.
More sustainable chemical activation strategies for the production of porous carbons
.
ChemSusChem
2021
;
14
:
94
117
.

97

Jiang-li
SHI
,
Chang
M.
Preparation and characterization of spinnable mesophase pitches: A review
.
New Carbon Mater
2019
;
34
:
211
9
. https://linkinghub.elsevier.com/retrieve/pii/S0008622319306670, doi = 10.1016/j.carbon.2019.06.091.

98

Wampler
TP.
Applied Pyrolysis Handbook. CRC Press,
2007
.

99

Saebea
D
,
Ruengrit
P
,
Arpornwichanop
A
et al.
Gasification of plastic waste for synthesis gas production
.
Energy Rep
2020
;
6
:
202
7
. (The 6th International Conference on Energy and Environment Research—Energy and Environment: Challenges towards Circular Economy.)

100

Baird
T
,
Fryer
JR
,
Grant
B.
Carbon formation on iron and nickel foils by hydrocarbon pyrolysis—reactions at 700°C
.
Carbon
1974
;
12
:
591
602
.

101

Boehm
HP
,
Clauss
A
,
Fischer
GO
et al.
The adsorption behavior of very thin carbon films
.
J Inorganic Gen Chem
1962
:
316
:
119
27
.

102

Wallace
PR.
The band theory of graphite
.
Phys Rev
1947
;
71
:
622
34
.

103

Brodie
BC.
.
II. On the atomic weight of graphite
.
Proc R Soc Lond
1860
;
10
:
11
2
.

104

Novoselov
KS
,
Geim
AK
,
Morozov
SV
et al.
Electric field effect in atomically thin carbon films
.
Science
2004
;
306
:
666
9
.

105

Cassell
AM
,
Raymakers
JA
,
Kong
J
et al.
Large scale cvd synthesis of single-walled carbon nanotubes
.
J Phys Chem B
1999
;
103
:
6484
92
.

106

Zou
JZ
,
Zeng
XR
,
Xiong
XB
et al.
Preparation of vapor grown carbon fibers by microwave pyrolysis chemical vapor deposition
.
Carbon
2007
;
45
:
828
32
.

107

Kumar
M
,
Ando
Y.
Chemical vapor deposition of carbon nanotubes: A review on growth mechanism and mass production
.
J Nanosci Nanotechnol
2010
;
10
:
3739
58
.

108

Huang
S
,
Maynor
B
,
Cai
X
et al.
Ultralong, well-aligned single-walled carbon nanotube architectureson surfaces
.
Adv Mater
2003
;
15
:
1651
5
.

109

Kleckley
S
,
Wang
H
,
Oladeji
I
et al. Fullerenes and Polymers Produced by the Chemical Vapor Deposition Method, Vol. 681 of ACS Symposium Series. American Chemical Society,
1997
,
51
60
.

110

Dong
G
,
van Baarle
DW
,
Frenken
JWM.
Chapter 2—Graphene formation on metal surfaces investigated by in-situ STM. In:
Aliofkhazraei
M
(ed.),
Advances in Graphene Science
,
Rijeka
:
IntechOpen
,
2013
.

111

Kalita
G
,
Tanemura
M
. Chapter 3—Fundamentals of chemical vapor deposited graphene and emerging applications. In: Kyzas GZ and Mitropoulos AC (eds), Graphene Materials. Rijeka: IntechOpen,
2017
.

112

Avouris P, Dimitrakopolous C. Graphene: synthesis and applications
.
Mater Today
2012
;
15
:
86
97
.

113

Wang
JB
,
Ren
Z
,
Hou
Y
et al.
A review of graphene synthesis at low temperatures by CVD methods
.
New Carbon Mater
2020
;
35
:
193
208
.

114

Bilisik
K
,
Akter
M.
Graphene nanocomposites: A review on processes, properties, and applications
.
J Ind Textiles
2021
;152808372110242.

115

Drogowska-Horna
K
,
Frank
O
,
Kalbac
M.
Chapter 10—Chemical vapor deposition (CVD) growth of graphene films. In:
Skakalova
V
and
Kaiser
AB
(eds),
Graphene
. 2nd edn.
Woodhead Publishing Series in Electronic and Optical Materials. Woodhead Publishing
,
2021
,
199
222
.

116

Ma
L-P
,
Ren
W
,
Cheng
H-M.
Transfer methods of graphene from metal substrates: A review
.
Small Methods
2019
;
3
:
1900049
.

117

Saeed
M
,
Alshammari
Y
,
Majeed
SA
et al.
Chemical vapour deposition of graphene—synthesis, characterisation, and applications: A review
.
Molecules
2020
;
25
.

118

Haddon
RC.
Carbon nanotubes
.
Acc Chem Res
2002
;
35
:
997
.

119

Oberlin
A
,
Endo
M
,
Koyama
T.
Filamentous growth of carbon through benzene decomposition
.
J Crystal Growth
1976
;
32
:
335
49
.

120

Lee
CJ
,
Park
J
,
Yu
JA.
Catalyst effect on carbon nanotubes synthesized by thermal chemical vapor deposition
.
Chem Phys Lett
2002
;
360
:
250
5
.

121

Awasthi
K
,
Srivastava
A
,
Srivastava
ON.
Synthesis of carbon nanotubes
.
J Nanosci Nanotechnol
2005
;
5
:
1616
36
.

122

Oncel
C
,
Yurum
Y.
Carbon nanotube synthesis via the catalytic CVD method: A review on the effect of reaction parameters
.
Fuller Nanotub Carbon Nanostruct
2006
;
14
:
17
37
.

123

Liu
Y
,
He
J
,
Zhang
N
et al.
Advances of microwave plasma-enhanced chemical vapor deposition in fabrication of carbon nanotubes: a review
.
J Mater Sci
2021
;
56
:
12559
83
.

124

Wang
X-D
,
Vinodgopal
K
,
Dai
G-P.
Synthesis of carbon nanotubes by catalytic chemical vapor Deposition. In:
El-Din Saleh
H
,
Mohamed El-Sheikh
SM
(eds),
Perspective of Carbon Nanotubes. IntechOpen
,
2019
.

125

Saputri
DD
,
Janah
AM
,
Saraswati
TE.
Synthesis of carbon nanotubes (CNT) by chemical vapor deposition (CVD) using a biogas-based carbon precursor: a review
.
IOP Conf Ser Mater Sci Eng
2020
;
959
:
012019
.

126

Pant
M
,
Singh
R
,
Negi
P
et al.
A comprehensive review on carbon nano-tube synthesis using chemical vapor deposition
.
Mater Today Proc
2021
;46(20):
11250
11253
.

127

Shoukat
R
,
Khan
MI.
Carbon nanotubes: a review on properties, synthesis methods and applications in micro and nanotechnology
.
Microsyst Technol
,
2021
.

128

Ishioka
M
,
Okada
T
,
Matsubara
K
et al.
Formation of vapor-grown carbon fibers in CO-CO2-H2 mixtures, II. Influence of catalyst
.
Carbon
1992
;
30
:
865
8
.

129

Ishioka
M
,
Okada
T
,
Matsubara
K.
Preparation of vapor-grown carbon fibers by floating catalyst method in Linz-Donawitz converter gas: Influence of catalyst size
.
Carbon
1993
;
31
:
699
703
.

130

Baker
RTK.
Catalytic growth of carbon filaments
.
Carbon
1989
;
27
:
315
23
.

131

Mordkovich
VZ.
Carbon nanofibers: A new ultrahigh-strength material for chemical technology
.
Theor Found Chem Eng
2003
;
37
:
429
38
.

132

Endo
M
,
Kroto
HW.
Formation of carbon nanofibers
.
J Phys Chem
1992
;
96
:
6941
4
.

133

Yoon
YJ
,
Baik
HK.
Catalytic growth mechanism of carbon nanofibers through chemical vapor deposition
.
Diam Relat Mater
2001
;
10
:
1214
7
. (11th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide.)

134

Rodriguez
NM.
A review of catalytically grown carbon nanofibers
.
J Mater Res
1993
;
8
:
3233
50
.

135

Kim
YA
,
Hayashi
T
,
Endo
M
et al. Carbon nanofibers. In:
Vajtai
R
(ed.),
Springer Handbook of Nanomaterials
.
Berlin, Heidelberg
:
Springer
,
2013
,
233
62
.

136

Al-Saleh
MH
,
Sundararaj
U.
A review of vapor grown carbon nanofiber/polymer conductive composites
.
Carbon
2009
;
47
:
2
22
.

137

Zhou
G
,
Yao
H
,
Zhou
Y
et al.
Self-assembled complexes of graphene oxide and oxidized vapor-grown carbon fibers for simultaneously enhancing the strength and toughness of epoxy and multi-scale carbon fiber/epoxy composites
.
Carbon
2018
;
137
:
6
18
.

138

Lu
Y
,
Sun
DX
,
Qi
XD
et al.
Achieving ultrahigh synergistic effect in enhancing conductive properties of polymer composites through constructing the hybrid network of ‘rigid’ submicron vapor grown carbon fibers and ‘reelable’ carbon nanotubes
.
Composit Sci Technol
2020
;
193
:
108141
.

139

Buckley
JD
,
Edie
DD.
Carbon–Carbon Materials and Composites
,
Elsevier Science
,
1993
.

140

Ting
J-M
,
Lake
ML.
Vapor-grown carbon-fiber reinforced carbon composites
.
Carbon
1995
;
33
:
663
7
.

141

Dhakate
SR
,
Mathur
RB
,
Dhami
TL.
Development of vapor grown carbon fibers (VGCF) reinforced carbon/carbon composites
.
J Mater Sci
2006
;
41
:
4123
31
.

142

Figueiredo
JL
,
Bernardo
CA
,
Baker
RTK
et al.
Carbon Fibers Filaments and Composites. Nato Science Series E
.
Netherlands
:
Springer
,
2013
.

143

Qanati MV, Rasooli A
.
Microstructural and main mechanical properties of novalac based carbon–carbon composites as the pyrolysis heating rate
.
Ceramics Int.
,
2021
;47(19):
26808
26821
.

144

Endo
M
,
Kim
YA
,
Hayashi
T
et al.
Vapor-grown carbon fibers (VGCFs): Basic properties and their battery applications
.
Carbon
2001
;
39
:
1287
97
.

145

Nagaraju
M
,
Sekhar
SC
,
Arbaz
SJ
et al.
Solvothermal-derived nanoscale spinel bimetallic oxide particles rationally bridged with conductive vapor-grown carbon fibers for hybrid supercapacitors
.
Appl Surf Sci
2021
;
563
:
150223
.

146

Angus
JC
,
Will
HA
,
Stanko
WS.
Growth of diamond seed crystals by vapor deposition
.
J Appl Phys
1968
;
39
:
2915
22
.

147

Chauhan
SP
,
Angus
JC
,
Gardner
NC.
Kinetics of carbon deposition on diamond powder
.
J Appl Phys
1976
;
47
:
4746
54
.

148

Harigai
T
,
Degai
S
,
Sugie
Y
et al.
Improvement of drilling performance by overcoating diamond-like carbon films on diamond-coated drills for carbon fiber reinforced plastics processing
.
Vacuum
2021
;
183
:
109755
.

149

May
PW
,
Mankelevich
YA.
From ultrananocrystalline diamond to single crystal diamond growth in hot filament and microwave plasma-enhanced cvd reactors: a unified model for growth rates and grain sizes
.
J Phys Chem C
2008
;
112
:
12432
41
.

150

Wan
BQ
,
Sun
XY
,
Ma
HT
et al.
Plasma enhanced chemical vapor deposition of diamond coatings on CU–W and CU–WC composites
.
Surf Coatings Technol
2015
;
284
:
133
8
. (The 42nd International Conference on Metallurgical Coatings and Thin Films.)

151

Nemanich
RJ
,
Carlisle
JA
,
Hirata
A
et al.
CVD diamond—research, applications, and challenges
.
MRS Bull
,
2014
;
39
:
490
4
.

152

Li
JT
,
Stanford
MG
,
Chen
W
et al.
Laminated laser-induced graphene composites
.
ACS Nano
2020
;
14
:
7911
9
.

153

Robertson
J.
Properties of diamond-like carbon
.
Surf Coatings Technol
1992
;
50
:
185
203
.

154

Erdemir
A
,
Donnet
C.
Tribology of diamond-like carbon films: recent progress and future prospects
.
J Phys D Appl Phys
2006
;
39
:
R311
27
.

155

Polushin
NI
,
Laptev
AI
,
Spitsyn
BV
et al.
Deposition of boron-doped thin CVD diamond films from methane-triethyl borate-hydrogen gas mixture
.
Processes
2020
;
8
:
666
.

156

Chen
W
,
Li
W
,
Liu
F
et al.
Microstructure of boron doped diamond electrodes and studies on its basic electrochemical characteristics and applicability of dye degradation
.
J Environ Chem Eng
2020
;
8
:
104348
.

157

Pinault-Thaury
M-A
,
Stenger
I
,
Gillet
R
et al.
Attractive electron mobility in (113) n-type phosphorus-doped homoepitaxial diamond
.
Carbon
2021
;
175
:
254
8
.

158

Song
J-S
,
Park
YS
,
Kim
N-H.
Hydrophobic anti-reflective coating of plasma-enhanced chemical vapor deposited diamond-like carbon thin films with various thicknesses for dye-sensitized solar cells
.
Appl Sci
2021
;
11
(
1
):358.

159

Roy
RK
,
Lee
K-R.
Biomedical applications of diamond-like carbon coatings: A review
.
J Biomed Mater Res B Appl Biomater
2007
;
83B
:
72
84
.

160

Shahsavari
F
,
Ehteshamzadeh
M
,
Amin
MH
et al.
A comparative study of surface morphology, mechanical and tribological properties of dlc films deposited on CR and NI nanolayers
.
Ceramics Int
2020
;
46
:
5077
85
.

161

Gotze
A
,
Makowski
S
,
Kunze
T
et al.
Tetrahedral amorphous carbon coatings for friction reduction of the valve train in internal combustion engines
.
Adv Eng Mater
2014
;
16
:
1226
33
.

162

Dearnaley
G
,
Arps
JH.
Biomedical applications of diamond-like carbon (DLC) coatings: A review
.
Surf Coatings Technol
2005
;
200
:
2518
24
.

163

Zia
AW
,
Zhou
Z
,
Li
LK-Y.
Chapter 7—Structural, mechanical, and tribological characteristics of diamond-like carbon coatings. In:
Nguyen Tri
P
,
Rtimi
S
,
Ouellet Plamondon
CM
(eds),
Nanomaterials-Based Coatings—Micro and Nano Technologies
.
Elsevier
,
2019
,
171
94
.

164

Yasuoka
Y
,
Harigai
T
,
Oh
J-S
et al.
Diamond-like carbon films from CO source gas by RF plasma CVD method
.
Japan J Appl Phys
2014
;
54
:
01AD04
.

165

Al Mamun
MA
,
Furuta
H
,
Hatta
A.
Pulsed DC plasma CVD system for the deposition of DLC films
.
Mater Today Commun
2018
;
14
:
40
6
.

166

Tallant
DR
,
Parmeter
JE
,
Siegal
M
et al.
The thermal stability of diamond-like carbon
.
Diam Relat Mater
1995
;
4
:
191
9
.

167

Sahoo
S
,
Pradhan
SK
,
Jeevitha
M
et al.
A study of diamond like carbon/chromium films deposited by microwave plasma activated chemical vapor deposition
.
J Non-Crystal Solids
2014
;
386
:
14
8
.

168

Ruijun
Z
,
Hongtao
M.
Nano-mechanical properties and nano-tribological behaviors of nitrogen-doped diamond-like carbon (DLC) coatings
.
J Mater Sci
2006
;
41
:
1705
9
.

169

Schwarz
C
,
Heeg
J
,
Rosenberg
M
et al.
Investigation on wear and adhesion of graded SI/SIC/DLC coatings deposited by plasma-enhanced-CVD
.
Diam Relat Mater
2008
;
17
:
1685
8
. (Proceedings of Diamond 2007, the 18th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide.)

170

Lowe
J.
Chapter 11—Aerospace applications. In:
Long
AC
(ed),
Design and Manufacture of Textile Composites
.
Woodhead Publishing Series in Textiles. Woodhead Publishing
,
2005
,
405
23
.

171

Ahmad
H
,
Markina
AA
,
Porotnikov
MV
et al.
A review of carbon fiber materials in automotive industry
.
IOP Conf Ser Mater Sci Eng
2020
;
971
:
032011
.

172

Joosse
PA
,
van Delft
DRV
,
Kensche
C
et al.
Cost effective large blade components by using carbon fibers
.
J Solar Energy Eng
2002
;
124
:
412
8
.

173

Hashimoto
K
,
Imae
T.
The spinnability of aqueous polymer solutions
.
Polym J
1990
;
22
:
331
5
.

174

Liu
F
,
Wang
H
,
Xue
L
et al.
Effect of microstructure on the mechanical properties of pan-based carbon fibers during high-temperature graphitization
.
J Mater Sci
2008
;
43
:
4316
22
.

175

Anton
F
. Process and apparatus for preparing artificial threads. US Patent No. 1,975,504,
1934
.

176

Edie
DD
,
Dunham
MG.
Melt spinning pitch-based carbon fibers
.
Carbon
1989
;
27
:
647
55
. (Carbon Fibers and Composites.)

177

Yarin
AL
,
Koombhongse
S
,
Reneker
DH.
Taylor cone and jetting from liquid droplets in electrospinning of nanofibers
.
J Appl Phys
2001
;
90
:
4836
46
.

178

Liu
Y
,
Kumar
S.
Recent progress in fabrication, structure, and properties of carbon fibers
.
Polym Rev
2012
;
52
:
234
58
.

179

Rahaman
MSA
,
Ismail
AF
,
Mustafa
A.
A review of heat treatment on polyacrylonitrile fiber
.
Polym Degrad Stab
2007
;
92
:
1421
32
.

180

Oya
A
,
Yoshida
S
,
Alcaniz-Monge
J
et al.
Formation of mesopores in phenolic resin-derived carbon fiber by catalytic activation using cobalt
.
Carbon
1995
;
33
:
1085
90
.

181

Wang
S
,
Bai
J
,
Innocent
MT
et al.
Lignin-based carbon fibers: Formation, modification and potential applications
.
Green Energy Environ
,
2021
.

182

Dumanlı
AG
,
Windle
AH.
Carbon fibres from cellulosic precursors: A review
.
J Mater Sci
2012
;
47
:
4236
50
.

183

Tang
MM
,
Bacon
R.
Carbonization of cellulose fibers—I. Low temperature pyrolysis
.
Carbon
1964
;
2
:
211
20
.

184

Chand
S.
Review carbon fibers for composites
.
J Mater Sci
2000
;
35
:
1303
13
.

185

Frank
E
,
Ingildeev
D
,
Buchmeiser
MR.
Chapter 2—High-performance pan-based carbon fibers and their performance requirements. In:
Bhat
G
(ed.),
Structure and Properties of High-Performance Fibers, Woodhead Publishing Series in Textiles
.
Oxford: Woodhead Publishing
,
2017
,
7
30
.

186

Forintos
N
,
Czigany
T.
Multifunctional application of carbon fiber reinforced polymer composites: Electrical properties of the reinforcing carbon fibers—a short review
.
Compos B: Eng
2019
;
162
:
331
43
.

187

Karger-Kocsis
J
,
Mahmood
H
,
Pegoretti
A.
All-carbon multi-scale and hierarchical fibers and related structural composites: A review
.
Compos Sci Technol
2020
;
186
:
107932
.

188

Savage
G
,
Savage
GM
,
Savage
E.
Carbon–Carbon Composites. Chapman & Hall,
1993
.

189

Scarponi
C.
Chapter 13—Carbon–carbon composites in aerospace engineering. In:
Rana
S
,
Fangueiro
R
(eds),
Advanced Composite Materials for Aerospace Engineering
,
Woodhead Publishing
,
2016
,
385
412
.

190

Manocha
LM.
High performance carbon–carbon composites
.
Sadhana
2003
;
28
:
349
58
.

191

Huang
X.
Fabrication and properties of carbon fibers
.
Materials
2009
;
2
:
2369
403
.

192

Wazir
AH
,
Kakakhel
L.
Preparation and characterization of pitch-based carbon fibers
.
New Carbon Mater
2009
;
24
:
83
8
.

193

Naito
K
,
Tanaka
Y
,
Yang
J-M
et al.
Flexural properties of pan- and pitch-based carbon fibers
.
J Am Ceram Soc
2008
;
92
:
186
92
.

194

Otani
S.
On the carbon fiber from the molten pyrolysis products
.
Carbon
1965
;
3
:
31
8
.

195

Kershaw
JR.
The chemical composition of a coal-tar pitch
.
Polycycl Aromat Compd
1993
;
3
:
185
97
.

196

Endo
M.
Structure of mesophase pitch-based carbon fibres
.
J Mater Sci
1988
;
23
:
598
605
.

197

Liu
J
,
Chen
X
,
Liang
D
et al.
Development of pitch-based carbon fibers: a review
.
Energy Sources A: Recovery Util Environ Eff 2020
:
1
21
.

198

Goodhew
PJ
,
Clarke
AJ
,
Bailey
JE.
A review of the fabrication and properties of carbon fibres
.
Mater Sci Eng
1975
;
17
:
3
30
.

199

Park
SH
,
Kim
C
,
Yang
KS.
Preparation of carbonized fiber web from electrospinning of isotropic pitch
.
Synth Met
2004
;
143
:
175
9
.

200

Park
SH
,
Kim
C
,
Jeong
YI
et al.
Activation behaviors of isotropic pitch-based carbon fibers from electrospinning and meltspinning
.
Synth Met
2004
;
146
:
207
12
.

201

Shi
Z
,
Chong
C
,
Wang
J
et al.
Electrospun pitch/polyacrylonitrile composite carbon nanofibers as high performance anodes for lithium-ion batteries
.
Mater Lett
2015
;
159
:
341
4
.

202

Otani
S
,
Kokubo
Y
,
Koitabashi
T.
The preparation of highly-oriented carbon fiber from pitch material
.
Bull Chem Soc Jap
1970
;
43
:
3291
2
.

203

Edie
DD.
Pitch and mesophase fibers. In:
Figueiredo
JL
,
Bernardo
CA
,
Baker
RTK
et al. (eds),
Carbon Fibers Filaments and Composites
.
Dordrecht, The Netherlands
:
Springer
,
1990
,
43
72
.

204

Daulbayev
C
,
Kaidar
B
,
Sultanov
F
et al.
The recent progress in pitch derived carbon fibers applications. A review
.
South Afr J Chem Eng
2021
;
38
:
9
20
.

205

Ohnishi
T
,
Murase
I
,
Noguchi
T
et al.
Preparation of graphite film by pyrolysis of polymers
.
Synth Met
1987
;
18
:
497
502
. (Proceedings of the International Conference of Science and Technology of Synthetic Metals.)

206

Du
W.
From graphite to graphene: direct liquid-phase exfoliation of graphite to produce single- and few-layered pristine graphene
.
J Mater Chem A
,
2013
;
1
:
10592
606
.

207

Yoo
K
,
Takei
Y
,
Kim
S
et al.
Direct physical exfoliation of few-layer graphene from graphite grown on a nickel foil using polydimethylsiloxane with tunable elasticity and adhesion
.
Nanotechnology
2013
;
24
:
205302
.

208

Qian
M
,
Zhou
YS
,
Gao
Y
et al.
Production of few-layer graphene through liquid-phase pulsed laser exfoliation of highly ordered pyrolytic graphite
.
Appl Surf Sci
2012
;
258
:
9092
5
.

209

Betancur
AF
,
Ornelas-Soto
N
,
Garay-Tapia
AM
et al.
A general strategy for direct synthesis of reduced graphene oxide by chemical exfoliation of graphite
.
Mater Chem Phys
2018
;
218
:
51
61
.

210

Liu
F
,
Wang
C
,
Sui
X
et al.
Synthesis of graphene materials by electrochemical exfoliation: Recent progress and future potential
.
Carbon Energy
2019
;
1
:
173
99
.

211

Cooper
AJ
,
Wilson
NR
,
Kinloch
IA
et al.
Single stage electrochemical exfoliation method for the production of few-layer graphene via intercalation of tetraalkylammonium cations
.
Carbon
2014
;
66
:
340
50
.

212

Bourelle
E
,
Claude-montigny
B
,
Metrot
A.
Electrochemical exfoliation of HOPG in formic—sulfuric acid mixtures
.
Mol Cryst Liq Cryst Sci Technol A: Mol Cryst Liq Cryst
1998
;
310
:
321
6
.

213

Legall
H
,
Stiel
H
,
Nickles
P-V
et al. Applications of highly oriented pyrolytic graphite (HOPG) for X-ray diagnostics and spectroscopy. In:
Kyrala
GA
,
Gauthier
J-CJ
,
MacDonald
CA
et al. (eds),
Laser-Generated, Synchrotron, and Other Laboratory X-Ray and EUV Sources, Optics, and Applications II
. Vol. 5918.
International Society for Optics and Photonics, SPIE
,
2005
,
11
21
.

214

Legall
H
,
Stiel
H
,
Arkadiev
V
et al.
High spectral resolution X-ray optics with highly oriented pyrolytic graphite
.
Opt Express
2006
;
14
:
4570
6
.

215

Xiao
J
,
Zhang
L
,
Zhou
K
et al.
Anisotropic friction behaviour of highly oriented pyrolytic graphite
.
Carbon
2013
;
65
:
53
62
.

216

Kim
Y
,
Hong
M
,
Oh
H
et al.
Solid electrolyte interphase revealing interfacial electrochemistry on highly oriented pyrolytic graphite in a water-in-salt electrolyte
.
J Phys Chem C
2020
;
124
:
20135
42
.

217

Enoki
T
,
Suzuki
M
,
Endo
M.
Graphite Intercalation Compounds and Applications
.
Oxford University Press
,
2003
.

218

Kaspar
P
,
Sobola
D
,
Dallaev
R
et al.
Characterization of Fe2O3 thin film on highly oriented pyrolytic graphite by AFM, ellipsometry and XPS
.
Appl Surf Sci
2019
;
493
:
673
8
.

219

RE
Franklin
.
Crystallite growth in graphitizing and non-graphitizing carbons
.
Proc R Soc Lond A Math Phys Eng Sci
1951
;
209
:
196
218
.

220

Sharma
S
,
Kamath
R
,
Madou
M.
Porous glassy carbon formed by rapid pyrolysis of phenol-formaldehyde resins and its performance as electrode material for electrochemical double layer capacitors
.
J Anal Appl Pyrol
2014
;
108
:
12
8
.

221

Eckert
H
,
Levendis
YA
,
Flagan
RC.
Glassy carbons from poly(furfuryl alcohol) copolymers: structural studies by high-resolution solid-state nmr techniques
.
J Phys Chem
1988
;
92
:
5011
9
.

222

Pesin
LA.
Review structure and properties of glass-like carbon
.
J Mater Sci
2002
;
37
:
1
28
.

223

Van der Linden
WE
,
Dieker
JW.
Glassy carbon as electrode material in electro-analytical chemistry
.
Anal Chim Acta
1980
;
119
:
1
24
.

224

Tarvainen
T
,
Patiala
H
,
Tunturi
T
et al.
Bone growth into glassy carbon implants: A rabbit experiment
.
Acta Orthop Scand
1985
;
56
:
63
6
.

225

Tarvainen
UT
,
Tunturi
TO
,
Paronen
I
et al.
Glassy carbon implant as a bone graft substitute: An experimental study on rabbits
.
Clin Mater
1994
;
17
:
93
8
.

226

Angle
M
,
Blair
G
,
Maier
C
. Method for molding glass lenses,
1974
.

227

Plaza
MG
,
Pevida
C
,
Martın
CF
et al.
Developing almond shell-derived activated carbons as co2 adsorbents
.
Sep Purif Technol
2010
;
71
:
102
6
.

228

Singh
RK
,
Ruj
B
,
Sadhukhan
AK
et al.
Waste plastic to pyrolytic oil and its utilization in CI engine: Performance analysis and combustion characteristics
.
Fuel
2020
;
262
:
116539
.

229

Manocha
SM.
Porous carbons
.
Sadhana
2003
;
28
:
335
48
.

230

Rodrıguez-Reinoso
F
,
Molina-Sabio
M.
Activated carbons from lignocellulosic materials by chemical and/or physical activation: An overview. Carbon
1992
;
30
:
1111
8
.

231

Huang
SJ
,
Yu
YC
,
Lee
TY
et al.
Correlations and characterization of porous solids by fractal dimension and porosity
.
Phys A Statist Mech Appl
1999
;
274
:
419
32
.

232

Reza
MS
,
Yun
CS
,
Afroze
S
et al.
Preparation of activated carbon from biomass and its applications in water and gas purification, a review
.
Arab J Basic Appl Sci
2020
;
27
:
208
38
.

233

Rivera-Utrilla
J
,
Sanchez-Polo
M
,
Gomez-Serrano
V
et al.
Activated carbon modifications to enhance its water treatment applications. An overview
.
J Hazard Mater
2011
;
187
:
1
23
.

234

Altıntıg
E
,
Yenigun
M
,
Sarı
A
et al.
Facile synthesis of zinc oxide nanoparticles loaded activated carbon as an eco-friendly adsorbent for ultra-removal of malachite green from water
.
Environ Technol Innov
2021
;
21
:
101305
.

235

Mohamad Nor
N
,
Lau
LC
,
Lee
KT
et al.
Synthesis of activated carbon from lignocellulosic biomass and its applications in air pollution control—a review
.
J Environ Chem Eng
2013
;
1
:
658
66
.

236

Wang
H
,
Li
Z
,
Yahyaoui
S
et al.
Effective adsorption of dyes on an activated carbon prepared from carboxymethyl cellulose: Experiments, characterization and advanced modelling
.
Chem Eng J
2021
;
417
:
128116
.

237

Singh
G
,
Lakhi
KS
,
Sil
S
et al.
Biomass derived porous carbon for CO2 capture
.
Carbon
2019
;
148
:
164
86
.

238

Lu
W
,
Cao
X
,
Hao
L
et al.
Activated carbon derived from pitaya peel for supercapacitor applications with high capacitance performance
.
Mater Lett
2020
;
264
:
127339
.

239

Ukkakimapan
P
,
Sattayarut
V
,
Wanchaem
T
et al.
Preparation of activated carbon via acidic dehydration of durian husk for supercapacitor applications
.
Diam Relat Mater
2020
;
107
:
107906
.

240

Streit
AFM
,
Collazzo
GC
,
Druzian
SP
et al.
Adsorption of ibuprofen, ketoprofen, and paracetamol onto activated carbon prepared from effluent treatment plant sludge of the beverage industry
.
Chemosphere
2021
;
262
:
128322
.

241

Bernal
V
,
Giraldo
L
,
Moreno-Pirajan
JC.
Physicochemical properties of activated carbon: Their effect on the adsorption of pharmaceutical compounds and adsorbate–adsorbent interactions
.
Carbon
2018
;
4
(
4
):62.

242

Roy
GM.
Activated Carbon Applications in the Food and Pharmaceutical Industries
.
Taylor & Francis
,
1994
.

243

Maldonado
JR
,
Peckerar
M.
X-ray lithography: Some history, current status and future prospects
.
Microelectr Eng
2016
;
161
:
87
93
.

244

Yang
C
,
Cao
Q
,
Puthongkham
P
et al.
3D-printed carbon electrodes for neurotransmitter detection
.
Angew Chem Int Ed
2018
;
57
:
14255
9
.

245

Peng
Z
,
Lin
J
,
Ye
R
et al.
Flexible and stackable laser-induced graphene supercapacitors
.
ACS Appl Mater Interf
2015
;
7
:
3414
9
.

246

Mamleyev
ER
,
Falk
F
,
Weidler
PG
et al.
Polyaramid-based flexible antibacterial coatings fabricated using laser-induced carbonization and copper electroplating
.
ACS Appl Mater Interf
2020
;
12
:
53193
205
.

247

Cisquella-Serra
A
,
Gamero-Castano
M
,
Ferrer-Argemi
L
et al.
Controlled joule-heating of suspended glassy carbon wires for localized chemical vapor deposition
.
Carbon
2020
;
156
:
329
38
.

248

Mantis
I
,
Hemanth
S
,
Caviglia
C
et al.
Suspended highly 3D interdigitated carbon microelectrodes
.
Carbon
2021
;
179
:
579
89
.

249

Asif
A
,
Heiskanen
A
,
Emneus
J
et al.
Pyrolytic carbon nanograss electrodes for electrochemical detection of dopamine
.
Electrochim Acta
2021
;
379
:
138122
.

250

Mishra
R
,
Pramanick
B
,
Maiti
TK
et al.
Glassy carbon microneedles—new transdermal drug delivery device derived from a scalable c-MEMs process
.
Microsyst Nanoeng
2018
;
4
:
38
.

251

Hemanth
S
,
Caviglia
C
,
Keller
SS.
Suspended 3d pyrolytic carbon microelectrodes for electrochemistry
.
Carbon
2017
;
121
:
226
34
.

252

Romppainen
H
. Carbon nanotube modified pyrolyzed carbon 3D microelectrodes. Master’s thesis, School of Electrical Engineering, Aalto University,
2021
.

253

Goring
G
,
Dietrich
P-I
,
Blaicher
M
et al.
Tailored probes for atomic force microscopy fabricated by two-photon polymerization
.
Appl Phys Lett
2016
;
109
:
063101
.

254

Thiha
A
,
Ibrahim
F
,
Muniandy
S
et al.
All-carbon suspended nanowire sensors as a rapid highly-sensitive label-free chemiresistive biosensing platform
.
Biosens Bioelectr
2018
;
107
:
145
52
.

255

Hemanth
S
,
Halder
A
,
Caviglia
C
et al.
3D carbon microelectrodes with bio-functionalized graphene for electrochemical biosensing
.
Biosensors
2018
;
8
:
70
.

256

Burks
R
,
Walker
Z
,
O’Neill
C
et al.
Microfabrication of multi-layer glassy carbon microstructures through dye-doped negative photoresists
.
J Micromech Microeng
2019
;
29
:
125012
.

257

Vomero
M
,
Gueli
C
,
Zucchini
E
et al.
Flexible bioelectronic devices based on micropatterned monolithic carbon fiber mats
.
Adv Mater Technol
2020
;
5
:
1900713
.

258

Castagnola
E
,
Winchester Vahidi
N
,
Nimbalkar
S
et al.
In vivo dopamine detection and single unit recordings using intracortical glassy carbon microelectrode arrays
.
MRS Adv
2018
;
3
:
1629
34
.

259

Pramanick
B
,
Mandal
N
,
Mondal
D
et al. C-mems derived glassy carbon electrodes as sensitive electrochemical biosensors. In: 2018 IEEE SENSORS, IEEE,
2018
:
1
4
.

260

Vaca
S
,
Pilloni
O
,
Gomez
AR
et al.
Photolithographically-patterned c-MEMS graphene by carbon diffusion through nickel
.
Nanotechnology
2020
;
32
:
265302
.

261

Herlin
N
,
Bohn
I
,
Reynaud
C
et al.
Nanoparticles produced by laser pyrolysis of hydrocarbons: analogy with carbon cosmic dust
.
Astron Astrophys
1998
;
330
:
1127
35
.

262

Galvez
A
,
Herlin-Boime
N
,
Reynaud
C
et al.
Carbon nanoparticles from laser pyrolysis
.
Carbon
2002
;
40
:
2775
89
.

263

Ortelli
EE
,
Geiger
F
,
Lippert
T
et al.
UV-laser-induced decomposition of kapton studied by infrared spectroscopy
.
Macromolecules
2000
;
33
:
5090
7
.

264

Srinivasan
R
,
Braren
B.
Ultraviolet laser ablation of organic polymers
.
Chem Rev
1989
;
89
:
1303
16
.

265

Ortelli
EE
,
Geiger
F
,
Lippert
T
et al.
Pyrolysis of kapton® in air: An in situ drift study
.
Appl Spectrosc
2001
;
55
:
412
9
.

266

Schaaf
P.
Laser Processing of Materials: Fundamentals, Applications and Developments.
Springer Series in Materials Science
.
Berlin, Heidelberg: Springer
,
2010
.

267

Duy
LX
,
Peng
Z
,
Li
Y
et al.
Laser-induced graphene fibers
.
Carbon
2018
;
126
:
472
9
.

268

Lu
Y
,
Lyu
H
,
Richardson
AG
et al.
Flexible neural electrode array based-on porous graphene for cortical microstimulation and sensing
.
Sci Rep
2016
;
6
:
33526
.

269

Oliveira
A
,
Ordonez
JS
,
Vajari
DA
et al.
Laser-induced carbon pyrolysis of electrodes for neural interface systems
.
Eur J Trans Myol
2016
;
26
:
6062
.

270

Vomero
M
,
Oliveira
A
,
Ashouri
D
et al.
Graphitic carbon electrodes on flexible substrate for neural applications entirely fabricated using infrared nanosecond laser technology
.
Sci Rep
2018
;
8
:
14749
.

271

Rahimi
R
,
Ochoa
M
,
Yu
W
et al.
Highly stretchable and sensitive unidirectional strain sensor via laser carbonization
.
ACS Appl Mater Interf
2015
;
7
:
4463
70
.

272

Huang
L
,
Xu
S
,
Wang
Z
et al.
Self-reporting and photothermally enhanced rapid bacterial killing on a laser-induced graphene mask
.
ACS Nano
2020
;
14
:
12045
53
.

273

Ye
R
,
James
DK
,
Tour
JM.
Laser-induced graphene
.
Acc Chem Res
2018
;
51
:
1609
20
.

274

In
JB
,
Hsia
B
,
Yoo
J-H
et al.
Facile fabrication of flexible all solid-state micro-supercapacitor by direct laser writing of porous carbon in polyimide
.
Carbon
2015
;
83
:
144
51
.

275

Rahimi
R
,
Ochoa
M
,
Tamayol
A
et al.
Highly stretchable potentiometric pH sensor fabricated via laser carbonization and machining of carbon-polyaniline composite
.
ACS Appl Mater Interf
2017
;
9
:
9015
23
.

276

Wu
W
,
Liang
R
,
Lu
L
et al.
Preparation of superhydrophobic laser-induced graphene using taro leaf structure as templates
.
Surf Coat Technol
2020
;
393
:
125744
.

277

Cai
J
,
Lv
C
,
Watanabe
A.
Laser direct writing of high-performance flexible all-solid-state carbon micro-supercapacitors for an on-chip self-powered photodetection system
.
Nano Energy
2016
;
30
:
790
800
.

278

Shim
HC
,
Tran
CV
,
Hyun
S
et al.
Three-dimensional laser-induced holey graphene and its dry release transfer onto Cu foil for high-rate energy storage in lithium-ion batteries
.
Appl Surf Sci
2021
;
564
:
150416
.

279

Karimi
G
,
Lau
I
,
Fowler
M
et al.
Parametric study of laser-induced graphene conductive traces and their application as flexible heaters
.
Int J Energy Res
2021
;
45
:
13712
25
.

280

Santos
NF
,
Pereira
SO
,
Moreira
A
et al.
IR and UV laser-induced graphene: Application as dopamine electrochemical sensors
.
Adv Mater Technol
2021
;
6
:
2100007
.

281

Jeong
S-Y
,
Lee
J-U
,
Hong
S-M
et al.
Highly skin-conformal laser-induced graphene-based human motion monitoring sensor
.
Nanomaterials
2021
;
11
(
4
):951.

282

Lin
N
,
Chen
H
,
Wang
W
et al.
Laser-induced graphene/MoO2 core-shell electrodes on carbon cloth for integrated, high-voltage, and in-planar microsupercapacitors
.
Adv Mater Technol
2021
;
6
:
2000991
.

283

Dworzanski
JP
,
Meuzelaar
HLC.
Pyrolysis mass spectrometry methods. In:
Lindon
JC
(ed.),
Encyclopedia of Spectroscopy and Spectrometry
, 2nd edn.
Oxford
:
Academic Press
,
1999
,
2301
13
.

284

Boon
JJ.
Analytical pyrolysis mass spectrometry: new vistas opened by temperature-resolved in-source PYMS
.
Int J Mass Spectrom Ion Processes
1992
;
118–119
:
755
87
(Advances in Mass Spectrometry.)

285

Kusch
EP
,
Mohd
MA.
Advanced Gas Chromatography—Progress in Agricultural, Biomedical and Industrial Applications
.
InTech
,
2005
.

286

Kruge
MA
,
Gallego
JLR
,
Lara-Gonzalo
A
et al. Chapter 7—Environmental forensics study of crude oil and petroleum product spills in coastal and oilfield settings: Combined insights from conventional GC–MS, thermodesorption–GC–MS, and pyrolysis–GC–MS. In:
Stout
SA
,
Wang
Z
(eds),
Oil Spill Environmental Forensics Case Studies
.
Butterworth-Heinemann
,
2018
,
131
55
.

287

Lucejko
JJ
,
Tamburini
D
,
Modugno
F
et al.
Analytical pyrolysis and mass spectrometry to characterise lignin in archaeological wood
.
Appl Sci
2021
;
11
(
1
):240.

288

Simmleit
N
,
Schulten
H-R.
Analytical pyrolysis and environmental research
.
J Anal Appl Pyrol
1989
;
15
:
3
28
.

289

Hermabessiere
L
,
Himber
C
,
Boricaud
B
et al.
Optimization, performance, and application of a pyrolysis-GC/MS method for the identification of microplastics
.
Anal Bioanal Chem
2018
;
410
:
6663
76
.

290

Primpke
S
,
Fischer
M
,
Lorenz
C
et al.
Comparison of pyrolysis gas chromatography/mass spectrometry and hyperspectral FTIR imaging spectroscopy for the analysis of microplastics
.
Anal Bioanal Chem
2020
;
412
:
8283
98
.

291

Irwin
WJ
,
Slack
JA.
Analytical pyrolysis in biomedical studies. A review
.
Analyst
1978
;
103
:
673
704
.

292

Wang
FC-Y
,
Burleson
AD.
The development of pyrolysis—fast gas chromatography for analysis of synthetic polymers
.
J Chromatogr A
1999
;
833
:
111
9
.

293

Shedrinsky
AM
,
Wampler
TP
,
Indictor
N
et al.
Application of analytical pyrolysis to problems in art and archaeology: A review
.
J Anal Appl Pyrol
1989
;
15
:
393
412
.

294

Chiavari
G
,
Montalbani
S
,
Prati
S
et al.
Application of analytical pyrolysis for the characterisation of old inks
.
J Anal Appl Pyrol
2007
;
80
:
400
5
.

295

Saiz-Jimenez
C
,
Hermosin
B
,
Ortega-Calvo
JJ
et al.
Applications of analytical pyrolysis to the study of stony cultural properties
.
J Anal Appl Pyrol
1991
;
20
:
239
51
. (Proceedings of the 9th International Conference on Fundamental Aspects, Analytical Techniques, Processes and Applications of Pyrolysis.)

296

Herrera
M
,
Matuschek
G
,
Kettrup
A.
Fast identification of polymer additives by pyrolysis-gas chromatography/mass spectrometry
.
J Anal Appl Pyrol
2003
;
70
:
35
42
.

297

Kusch
P
,
Schroeder-Obst
D
,
Obst
V
et al. Chapter 17—application of pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) and scanning electron microscopy (SEM) in failure analysis for the identification of organic compounds in chemical, rubber, and automotive industry. In:
Makhlouf
ASH
,
Aliofkhazraei
M
(eds),
Handbook of Materials Failure Analysis with Case Studies from the Chemicals, Concrete and Power Industries
.
Butterworth-Heinemann
,
2016
,
441
69
.

298

Rehrah
D
,
Reddy
MR
,
Novak
JM
et al.
Production and characterization of biochars from agricultural by-products for use in soil quality enhancement
.
J Anal Appl Pyrol
2014
;
108
:
301
9
.

299

Huang
W-H
,
Lee
D-J
,
Huang
C.
Modification on biochars for applications: A research update
.
Bioresour Technol
2021
;
319
:
124100
.

300

Pan
J
,
Ma
J
,
Zhai
L
et al.
Achievements of biochar application for enhanced anaerobic digestion: A review
.
Bioresour Technol
2019
;
292
:
122058
.

301

Lewandowski
WM
,
Januszewicz
K
,
Kosakowski
W.
Efficiency and proportions of waste tyre pyrolysis products depending on the reactor type—a review
.
J Anal Appl Pyrol
2019
;
140
:
25
53
.

302

Widiyannita
AM
,
Cahyono
RB
,
Budiman
A
et al. Study of pyrolysis of ulin wood residues. In:
Proceedings of the 12th International Conference on Synchrotron Radiation Instrumentation—SRI2015
,
New York
,
NY, USA
,
2016
,
050004
. [Online; accessed 2019-12-25].

303

Williams
PT.
Pyrolysis of waste tyres: A review
.
Waste Manag
2013
;
33
:
1714
28
.

304

Jung
S-H
,
Cho
M-H
,
Kang
B-S
et al.
Pyrolysis of a fraction of waste polypropylene and polyethylene for the recovery of BTX aromatics using a fluidized bed reactor
.
Fuel Process Technol
2010
;
91
:
277
84
.

305

Hwang
I-H
,
Kobayashi
J
,
Kawamoto
K.
Characterization of products obtained from pyrolysis and steam gasification of wood waste, RDF, and RPF
.
Waste Manag
2014
;
34
:
402
10
.

306

Ucar
S
,
Karagoz
S
,
Ozkan
AR
et al.
Evaluation of two different scrap tires as hydrocarbon source by pyrolysis
.
Fuel
2005
;
84
:
1884
92
.

307

[Anuar Sharuddin
SD
,
Abnisa F, [Wan Daud] WMA et al. A review on pyrolysis of plastic wastes
.
Energy Convers Manag
2016
;
115
:
308
26
.

308

Debono
O
,
Villot
A.
Nitrogen products and reaction pathway of nitrogen compounds during the pyrolysis of various organic wastes
.
J Anal Appl Pyrol
2015
;
114
:
222
34
.

309

Mohan
D
,
Pittman
CU
,
Steele
PH.
Pyrolysis of wood/biomass for bio-oil: A critical review
.
Energy Fuels
2006
;
20
:
848
89
.

310

Lopez
A
,
De Marco
I
,
Caballero
BM
et al.
Pyrolysis of municipal plastic wastes II: Influence of raw material composition under catalytic conditions
.
Waste Manag
2011
;
31
:
1973
83
.

311

Muhammad
C
,
Onwudili
JA
,
Williams
PT.
Catalytic pyrolysis of waste plastic from electrical and electronic equipment
.
J Anal Appl Pyrol
2015
;
113
:
332
9
.

312

Wang
J
,
Nie
P
,
Ding
B
et al.
Biomass derived carbon for energy storage devices
.
J Mater Chem A
2017
;
5
:
2411
28
.

313

Yu
K
,
Li
J
,
Qi
H
et al.
High-capacity activated carbon anode material for lithium-ion batteries prepared from rice husk by a facile method
.
Diam Relat Mater
2018
;
86
:
139
45
.

314

Hyun
JC
,
Kwak
JH
,
Lee
ME
et al.
Intensification of pseudocapacitance by nanopore engineering on waste-bamboo-derived carbon as a positive electrode for lithium-ion batteries
.
Materials
2019
;
12
:
2733
.

315

Sun
N
,
Liu
H
,
Xu
B.
Facile synthesis of high performance hard carbon anode materials for sodium ion batteries
.
J Mater Chem A
2015
;
3
:
20560
6
.

316

Gao
G
,
Cheong
L-Z
,
Wang
D
et al.
Pyrolytic carbon derived from spent coffee grounds as anode for sodium-ion batteries
.
Carbon Resourc Convers
2018
;
1
:
104
8
.

317

Teo
EYL
,
Muniandy
L
,
Ng
E-P
et al.
High surface area activated carbon from rice husk as a high performance supercapacitor electrode
.
Electrochim Acta
2016
;
192
:
110
9
.

318

Ahmed
S
,
Ahmed
A
,
Rafat
M.
Supercapacitor performance of activated carbon derived from rotten carrot in aqueous, organic and ionic liquid based electrolytes
.
J Saudi Chem Soc
2018
;
22
:
993
1002
.

319

Mensah-Darkwa
K
,
Zequine
C
,
Kahol
PK
et al.
Supercapacitor energy storage device using biowastes: A sustainable approach to green energy
.
Sustainability
2019
;
11
:
414
.

320

Sun
L
,
Tian
C
,
Li
M
et al.
From coconut shell to porous graphene-like nanosheets for high-power supercapacitors
.
J Mater Chem A
2013
;
1
:
6462
70
.

321

Chen
H
,
Guo
Y-C
,
Wang
F
et al.
An activated carbon derived from tobacco waste for use as a supercapacitor electrode material
.
New Carbon Mater
2017
;
32
:
592
9
.

322

Thirumal
V
,
Dhamodharan
K
,
Yuvakkumar
R
et al.
Cleaner production of tamarind fruit shell into bio-mass derived porous 3d-activated carbon nanosheets by CVD technique for supercapacitor applications
.
Chemosphere
2021
;
282
:
131033
.

323

Xu
S.
One-step fabrication of carbon fiber derived from waste paper and its application for catalyzing tri-iodide reduction
.
IOP Conf Ser: Earth Environ Sci
2017
;
52
:
012014
.

324

Ma
P
,
Lu
W
,
Yan
X
et al.
Heteroatom tri-doped porous carbon derived from waste biomass as pt-free counter electrode in dye-sensitized solar cells
.
RSC Adv
2018
;
8
:
18427
33
.

325

Dasari
KK
,
Gumtapure
V.
Activated carbon-based dye-sensitized solar cell for development of highly sensitive temperature and current sensor
.
Mater Res Exp
2019
;
6
:
085531
.

326

Aftabuzzaman
M
,
Kim
HK.
Porous carbon materials as supreme metal-free counter electrode for dye-sensitized solar cells
.
Emerg Sol Energy Mater
2018
;4 [online; accessed 2019-12-30].

327

Siong
Y
,
Atabaki
M
,
Idris
J.
Performance of activated carbon in water filters
.
Water Resourc
2013
:
1
19
.

328

Ahmedna
M
,
Marshall
WE
,
Husseiny
AA
et al.
The use of nutshell carbons in drinking water filters for removal of trace metals
.
Water Res
2004
;
38
:
1062
8
.

329

Depci
T
,
Kul
AR
,
Onal
Y.
Competitive adsorption of lead and zinc from aqueous solution on activated carbon prepared from van apple pulp: Study in single- and multi-solute systems
.
Chem Eng J
2012
;
200–202
:
224
36
.

330

Gupta
VK
,
Srivastava
SK
,
Mohan
D
et al.
Design parameters for fixed bed reactors of activated carbon developed from fertilizer waste for the removal of some heavy metal ions
.
Waste Manag
1998
;
17
:
517
22
.

331

Ozsin
G
,
Kılıc
M
,
Apaydın-Varol
E
et al.
Chemically activated carbon production from agricultural waste of chickpea and its application for heavy metal adsorption: equilibrium, kinetic, and thermodynamic studies
.
Appl Water Sci 2019
;
9
:
56
.

332

Al-Malack
MH
,
Basaleh
AA.
Adsorption of heavy metals using activated carbon produced from municipal organic solid waste
.
Desalin Water Treat
2016
;
57
:
24519
31
.

333

Anirudhan
TS
,
Sreekumari
SS.
Adsorptive removal of heavy metal ions from industrial effluents using activated carbon derived from waste coconut buttons
.
J Environ Sci
2011
;
23
:
1989
98
.

334

Chen
T
,
Zhang
Y
,
Wang
H
et al.
Influence of pyrolysis temperature on characteristics and heavy metal adsorptive performance of biochar derived from municipal sewage sludge
.
Bioresourc Technol
2014
;
164
:
47
54
.

335

Pramanick
B
,
Cadenas
LB
,
Kim
D-M
et al.
Human hair-derived hollow carbon microfibers for electrochemical sensing
.
Carbon
2016
;
107
:
872
7
.

336

Ayyalusamy
S
,
Mishra
S
,
Suryanarayanan
V.
Promising post-consumer pet-derived activated carbon electrode material for non-enzymatic electrochemical determination of carbofuran hydrolysate
.
Sci Rep
2018
;
8
:
1
9
.

337

Sudha
V
,
Senthil Kumar
SM
,
Thangamuthu
R.
Hierarchical porous carbon derived from waste amla for the simultaneous electrochemical sensing of multiple biomolecules
.
Colloids Surf B: Biointerf
2019
;
177
:
529
40
.

338

Akshaya
KB
,
Bhat
VS
,
Varghese
A
et al.
Non-enzymatic electrochemical determination of progesterone using carbon nanospheres from onion peels coated on carbon fiber paper
.
J Electrochem Soc
2019
;
166
:
B1097
106
.

339

Bhat
VS
,
Supriya
S
,
Hegde
G.
Review—biomass derived carbon materials for electrochemical sensors
.
J Electrochem Soc
2020
;
167
:
037526
.

340

Zuniga-Muro
NM
,
Bonilla-Petriciolet
A
,
Mendoza-Castillo
DI
et al.
Recycling of tetra pak wastes via pyrolysis: Characterization of solid products and application of the resulting char in the adsorption of mercury from water
.
J Clean Product
2021
;
291
:
125219
.

341

Jagdale
P
,
Koumoulos
EP
,
Cannavaro
I
et al.
Towards green carbon fibre manufacturing from waste cotton: a microstructural and physical property investigation
.
Manuf Rev
2017
;
4
:
10
.

342

Fernandez
A
,
Lopes
CS
,
Gonzalez
C
et al. .
Khanna
R
and
Cayumil
R
(Ed), Characterization of carbon fibers recovered by pyrolysis of cured prepregs and their reuse in new composites. In
Recent Developments in the Field of Carbon Fibers
, IntechOpen, Vol.
7
,
2018
,. [Online; accessed 2019-12-30].

343

Lopez
FA
,
Rodr-ıguez
O
,
Alguacil
FJ
et al.
Recovery of carbon fibres by the thermolysis and gasification of waste prepreg
.
J Anal Appl Pyrol
2013
;
104
:
675
83
.

344

Yousef
S
,
Eimontas
J
,
Subadra
SP
et al.
Functionalization of char derived from pyrolysis of metallised food packaging plastics waste and its application as a filler in fiberglass/epoxy composites
.
Process Saf Environ Protect
2021
;
147
:
723
33
.

345

Yousef
S
,
Kalpokaite-Dickuviene
R
,
Baltusnikas
A
et al.
A new strategy for functionalization of char derived from pyrolysis of textile waste and its application as hybrid fillers (CNTs/char and graphene/char) in cement industry
.
J Clean Prod
2021
;
314
:
128058
.

346

Sınag
A
,
Gulbay
S
,
Uskan
B
et al.
Production and characterization of pyrolytic oils by pyrolysis of waste machinery oil
.
J Hazard Mater
2010
;
173
:
420
6
.

347

Miandad
R
,
Rehan
M
,
Barakat
MA
et al.
Catalytic pyrolysis of plastic waste: Moving toward pyrolysis based biorefineries
.
Front Energy Res
2017
;
7
:
27
.

348

Li
Q
,
Faramarzi
A
,
Zhang
S
et al.
Progress in catalytic pyrolysis of municipal solid waste
.
Energy Convers Manag
2020
;
226
:
113525
.

349

Miandad
R
,
Barakat
MA
,
Aburiazaiza
AS
et al.
Catalytic pyrolysis of plastic waste: A review
.
Process Saf Environ Protect
2016
;
102
:
822
38
.

350

Boehm
HP
,
Fitzer
E
,
Kochling
K-H
et al.
Recommended terminology for the description of carbon as a solid
.
Pure Appl Chem
1995
;
67
:
473
506
.

351

Brooks
JD
,
Taylor
GH.
The formation of graphitizing carbons from the liquid phase
.
Carbon
1965
;
3
:
185
93
.

352

Marsh
H
,
Diez
MA.
Mesophase of Graphitizable Carbons
.
New York (NY)
:
Springer
,
1994
,
231
57
.

353

Wang
G
,
Eser
S.
Molecular composition of the high-boiling components of needle coke feedstocks and mesophase development
.
Energy Fuels
2007
;
21
:
3563
72
.

354

Blanco
C
,
Santamaria
R
,
Bermejo
J
et al.
Microstructure and properties of pitch-based carbon composites
.
J Microsc
1999
;
196
:
213
24
.

355

Ji
SJ
,
Cheng
XL
,
Zhao
JH
et al. Preparation of mesocarbon microbeads (MCMB) from suspensions of a synthetic naphthalene isotropic pitch. Vol. 753 of Key Engineering Materials.
Trans Tech Publications Ltd
,
2017
,
231
6
. https://www.scientific.net/KEM.753.231.

356

Chen
Q
,
Nie
Y
,
Li
T
et al.
Electrochemical performance of novel mesocarbon microbeads as lithium ion battery anode
.
J Mater Sci Mater Electron
2018
;
29
:
14788
95
.

357

Song
L-J
,
Liu
S-S
,
Yu
B-J
et al.
Anode performance of mesocarbon microbeads for sodium-ion batteries
.
Carbon
2015
;
95
:
972
7
.

358

Wang
F
,
Jiao
S
,
Liu
W
et al.
Preparation of mesophase carbon microbeads from fluidized catalytic cracking residue oil: The effect of active structures on their coalescence
.
J Anal Appl Pyrol
2021
;
156
:
105166
.

359

Gao
N
,
Cheng
B
,
Hou
H
et al.
Mesophase pitch based carbon foams as sound absorbers
.
Mater Lett
2018
;
212
:
243
6
.

360

Wang
Y
,
He
Z
,
Zhan
L
et al.
Coal tar pitch based carbon foam for thermal insulating material
.
Mater Lett
2016
;
169
:
95
8
.

361

Tzvetkov
G
,
Tsyntsarski
B
,
Balashev
K
et al.
Microstructural investigations of carbon foams derived from modified coal-tar pitch
.
Micron
2016
;
89
:
34
42
.

362

Li
S
,
Lin
B-F
,
Tzeng
S-S
et al.
Structure and properties of mesophase pitch-derived carbon foams reinforced by mesocarbon microbeads
.
Int J Mater Res
2016
;
107
:
148
57
.

363

Casco
ME
,
Martınez-Escandell
M
,
Kaneko
K
et al.
Very high methane uptake on activated carbons prepared from mesophase pitch: A compromise between microporosity and bulk density
.
Carbon
2015
;
93
:
11
21
.

364

Cao
B
,
Liu
H
,
Xu
B
et al.
Mesoporous soft carbon as an anode material for sodium ion batteries with superior rate and cycling performance
.
J Mater Chem A
2016
;
4
:
6472
8
.

365

Zhu
Y
,
Zhao
C
,
Xu
Y
et al.
Preparation and characterization of coal pitch-based needle coke (part i): The effects of aromatic index (fa) in refined coal pitch
.
Energy Fuels
2019
;
33
:
3456
64
.

366

Barreda
D
,
Perez-Mas
AM
,
Silvestre-Albero
A
et al.
Unusual flexibility of mesophase pitch-derived carbon materials: An approach to the synthesis of graphene
.
Carbon
2017
;
115
:
539
45
.

367

Liu
M
,
Li
W
,
Ruan
S
et al.
N-doped hierarchical mesoporous carbon from mesophase pitch and polypyrrole for supercapacitors
.
Energy Fuels
2020
;
34
:
5044
51
.

368

Mukhopadhyay
TK
,
Leherte
L
,
Datta
A.
Molecular mechanism for the self-supported synthesis of graphitic carbon nitride from urea pyrolysis
.
J Phys Chem Lett
2021
;
12
:
1396
406
.

369

Xu
Y
,
Zhang
X
,
Chen
Z
et al.
Chemical vapor deposition of amorphous molybdenum sulphide on black phosphorus for photoelectrochemical water splitting
.
J Mater Sci Technol
2021
;
68
:
1
7
.

370

McElwee-White
L.
Design of precursors for the CVD of inorganic thin films
.
Dalton Trans
2006
;
5327
33
.

371

Konstantinov
K
,
Stambolova
I
,
Peshev
P
et al.
Preparation of ceria films by spray pyrolysis method
.
Int J Inorgan Mater
2000
;
2
:
277
80
.

372

Perednis
D
,
Gauckler
LJ.
Thin film deposition using spray pyrolysis
.
J Electroceram
2005
;
14
:
103
11
.

373

Mooney
JB
,
Radding
SB.
Spray pyrolysis processing
.
Annu Rev Mater Sci
1982
;
12
:
81
101
.

374

Viguie
JC.
Chemical vapor deposition at low temperatures
.
J Electrochem Soc
1975
;
122
:
585
.

375

Krishnakumar
R
,
Subramanian
V
,
Ramprakash
Y
et al.
Thin film preparation by spray pyrolysis for solar cells
.
Mater Chem Phys
1987
;
16
:
385
95
.

376

Mollmann
A
,
Gedamu
D
,
Vivo
P
et al.
Highly compact TiO2 films by spray pyrolysis and application in perovskite solar cells
.
Adv Eng Mater
2019
;
21
:
1801196
.

377

Sayed
MH
,
Robert
EVC
,
Dale
PJ
et al.
Cu2SNS3 based thin film solar cells from chemical spray pyrolysis
.
Thin Solid Films
2019
;
669
:
436
9
.

378

Onofre
YJ
,
Catto
AC
,
Bernardini
S
et al.
Highly selective ozone gas sensor based on nanocrystalline Zn0.95Co0.05O thin film obtained via spray pyrolysis technique
.
Appl Surf Sci
2019
;
478
:
347
54
.

379

Szymczewska
D
,
Chrzan
A
,
Karczewski
J
et al.
Spray pyrolysis of doped-ceria barrier layers for solid oxide fuel cells
.
Surf Coatings Technol
2017
;
313
:
168
76
.

380

Ye
Z
,
Yang
J
,
Li
B
et al.
Amorphous molybdenum sulfide/carbon nanotubes hybrid nanospheres prepared by ultrasonic spray pyrolysis for electrocatalytic hydrogen evolution
.
Small
2017
;
13
:
1700111
.

381

Kelesidis
GA
,
Pratsinis
SE.
A perspective on gas-phase synthesis of nanomaterials: Process design, impact and outlook
.
Chem Eng J
2021
;
421
:
129884
.

382

Phakatkar
AH
,
Saray
MT
,
Rasul
MG
et al.
Ultrafast synthesis of high entropy oxide nanoparticles by flame spray pyrolysis
.
Langmuir
2021
;37(30):
9059
9068
.

383

Resende
FLP.
Recent advances on fast hydropyrolysis of biomass
.
Catal Today
2016
;
269
:
148
55
. (Transformations of Biomass and its Derivatives to Fuels and Chemicals.)

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.